Four friends sit by the pool at a Cancún resort. Amy (Jena Malone) and Stacey (Laura Ramsey), two best friends, are on vacation with their boyfriends Jeff (Jonathan Tucker) and Eric (Shawn Ashmore). When Amy realizes that she has lost an earring, a boy Mathias (Joe Anderson) finds it at the bottom of the pool and returns it to her. Grateful, they invite him to share a drink with them, and Hans ends up inviting them to join him and his friend Dimitri (Dimitri Baveas) on a visit to an ancient ruin that his brother and wife are excavating.When the cousins working the dig don't show up the next morning to pick them up, the six have difficulty finding a taxi to take them to the ruins, and end up paying a local truck driver (Patricio Almeida Rodríguez) to take them there. At the edge of the jungle, they find the brother's truck abandoned on a dirt road. Matheas looks confused, but they decide to go ahead and look for the ruins themselves. They wander through the jungle, until they finally come across a clearing, and a high ancient ruin stands before them. While they all stand raptured at this hidden secret, the sound of horses and shouting men suddenly comes from behind them.The six vacationers turn around in surprise, and repeatedly try to find out what they clearly have done wrong. Men emerge from the jungle with bows and arrows, and an older man (Sergio Calderón) in the middle holds a silver revolver, staring them down. Amy stands in the back with her camera, and is instinctively taking pictures with her camera, not realizing how much danger they are in. The men instantly turn violent, and when Dimitri tries to hand over the camera in a sign of apology, he is shot in the chest with an arrow, and then shot in the face. Astounded, the friends retreat back from the men, up the ruins. Strangely enough, the men do not follow them, but do not leave the clearing.At the top of the summit, Matheas scrambles around looking for his cousins in the tents that they discovered. The others check their phones, but can't get a signal. Matheas finds the tents unpacked, but there is no sign of his cousin. Coming from the bottom of a deep shaft in the middle of the summit, they hear a cell phone ringing faintly. Desperate for a phone, Matheas loops a rope around him, and the other boys lower him slowly down the shaft by an overhead crank. It is slow going, until suddenly the rope snaps and Matheas plunges to the bottom.While the boys repair the rope, Stacey volunteers to go down the shaft after Matheas and the phone. They lower her slowly down the line, but it isn't quite long enough to take her all of the way. Stacey unhooks herself from the rope to drop to the dirt floor, but lands on a lantern with her knee. Having to pull out a shard of glass from her knee, Stacey winces and hobbles towards Matheas. He says that he is scared, and can't feel his legs. It's clear that his back is broken, so the remainder on the surface fashion a back-board to load him up on. Now it is Amy's turn to be lowered into the shaft; at the bottom, she and Stacey struggle to hoist Matheas on the backboard. All are lifted to the surface, and they survey the damage. While Jeff, a pre-med student, inspects Matheas' wounds, they all argue about what to do about their situation.Amy, at her wit's end, storms down the steps of the ruins to confront their captors. When she reaches the bottom and yells at them to help, they shout back in a language that she doesn't understand. Jeff runs to drag her away from the men, and out of frustration and anger, Amy rips a large chunk of some of the vines that cover the ruins and throws it at the menacing men. It hits a small boy and harmlessly falls to his feet, but the captors quickly turn their attention to the little boy, and shout at him, gesturing towards the ruins. The boy cries in protest, and after refusing to move, he is shot with bows and arrows down to the ground, while his mother looks on.Jeff and Amy run back to the summit, and report back what they saw to Stacey and Eric. They are all completely confused, and decide to go to sleep in the tent to wait for someone to come find them. In the morning, Stacey wakes up screaming. She looks down at her leg, and one of the vines from the ruins is clearly growing into the large cut she had on her knee. Screaming to have it taken out, Chris quickly goes to pull out the vine - and removes about a foot of greenage from her leg. They call for Jeff to take a look, while Amy stands by Matheas to check on him. Sweating and looking gray, Matheas asks Amy to pull the blanket from off of his body - he senses something is wrong with his legs. She obliges and screams as well, when they see that a massive amount of vines has sprouted overnight all over his lower half. They try to remove it the best they can, but he is severely injured and has cuts all over his skin. Amy knows what is going on now; they are being quarantined from whatever evil lurks in the ruins.The cell phone rings again from the shaft, and Stacey and Amy once again descend into the shaft to look for it. Armed with handmade torches, they begin a search of the inside, which is covered in the ominous vines. As they walk slowly down a hall, they hear the phone ringing again - a high pitched call. A woman lies with her back to them against a wall, and when they touch her, her body falls to the side and the friends scream. Calming themselves to continue with the search, Amy stares at one of the red flowers that now adorn the vines. As she gets closer, you can see that the inside of the red flower is vibrating. It, along with the other flowers, are actually recreating the sound of a cell phone ring by vibrating their stamens. Mesmerized, she goes to touch the flower, and the vines suddenly rear up in protest. The girls run to escape the vines' clutches, and are pulled up out of the shaft just in time.Explaining what happened to them in the shaft, Jeff inspects Matheas' wounds, and announces that there is no way that he will be able to survive if they don't amputate his legs immediately. Since help is not definite, Jeff says that there is no time to waste. Eric protests, and they put it to a vote. Unable to come to a consensus, Matheas weakly calls out to them that he wants them to do it. The girls go to the tent, while Jeff heats up a cast iron cooking pan in the fire. Eric is told to hold down Matheas, while Jeff breaks both leg bones and cuts them off with a hunting knife they found - and finally cauterizes them with the pan. Stacey and Amy clutch each other holding their ears, while they try to block out the screams.They come out when it is over, and watch as the vines retrieve the remaining flesh that Jeff had cut away. The vines are clearly carnivorous, and are waiting for them all to die. Another day gone by, Stacey and Amy go into one of the tents to try and sleep while Eric sits outside on watch. Amy can't sleep, and sits next to Eric while they talk about if they think Stacey is going to be alright. When Amy begins to cry, she leans her head into Eric's shoulder as they sit on a log. Stacey, inside the tent, awakens to the apparent moans and sighs that she believes is coming from Eric & Amy having sex. Furious, she storms out of the tent and accuses the both of them of sleeping together - insisting that she heard them.Amy and Eric both deny it, when Jeff walks up to see what the commotion is. Stacey screams at Amy, and when Jeff tries to intervene, she lashes out and tells him that Amy has cheated on him before. While the four friends argue, they leave Matheas un-guarded, and the vines come from the ruins and choke him. When they finally realize that they left him unattended, Jeff runs to his rescue, but is too late. The vines claim the remainder of his body.In the morning, Amy and Jeff sit next to each other at the top of the steps watching the sunrise. Eric emerges from his tent and asks Jeff to come see Stacey - it is clear that something is very wrong.They enter the tent, and Eric tells Stacey to show them her back. She lifts her shirt, and reveals a dark green patch growing under her skin, and a vine slithers like a snake under the surface. Outside, they decide that they have to cut it out of her. Amy clutches her while Stacey screams in agony. Jeff cuts a large gash by her knee, and grabs the vine that is attempting to burrow further into her leg. They ask her if she wants them to continue, and she cries out to tell them to keep going. They turn her on her back and Jeff makes a larger cut, pulling out foot after foot of vine from her back. Finally removed, they bandage her the best they can.Later, sitting by the fire, they each eat the last of the remaining food - four solitary grapes. Stacey seems slightly hysterical and insists that she can feel another one by her bones. Eric tells her that it's just in her head, but she then says that she can feel them in her head as well. They try and convince her that there isn't anything else in her body, and Amy offers her a pull from the bottle of tequila they found in the tent. Stacey drinks, and a flash of the wiggling vine shows up on her furrowed brow. The three friend's eyes open wide, and immediately look away so she can't see their reactions. Their silence says it all, and she tells them to cut again - Jeff says that there can't be anymore cutting - she has already lost too much blood.All four asleep, Stacey awakens first and ambles out of the tent. She hobbles along searching for the hunting knife that they used to cut out the vines the other day. Eric wakes up, and all three emerge from the tent to find Stacey standing in a pool of her own blood, slowly cutting herself to try and remove the invading weeds. They tell her to give them the knife - but she is clearly beyond reason. When Jeff tries to get her to hand it over, she lashes out and cuts him in the palm. Eric now tries to get her attention, and she turns and viciously buries the knife into his chest. Eric falls to the ground and dies from the knife wound, and the vines once again come forward to claim their meal. Stacey - screaming from the pain and realising what she has just done, begs Amy to kill her. While she begs, small vines wave from the cuts on her body. Amy looks pleadingly at Jeff, and Jeff quietly walks to Eric's body, and puts Stacey out of her misery.Jeff now smears blood on Amy's face and arms, and explains to her that she must run, while he creates a diversion. He walks down the steps holding her, presumably dead, in his arms, and lays her down on the ground. The men, still there, watch him warily, while Jeff starts a long tirade about himself and the people that they had let die. He wanders along the edge of the ruins, and on cue. Amy gets up suddenly and runs as fast as possible towards the abandoned Jeep they found earlier. The men shoot Jeff with several arrows, and the large man shoots him with the final bullet.Amy, chased by the men, incredibly manages to reach the Jeep and starts the car. She speeds away, down the road to an unknown fate. The next day, Demitris' two other friends that had planned to join them, entered the clearing, calling out their missing friend's name. - end***** BELOW IS THE SYNOPSIS OF THE BOOK *****On vacation in Cancun, six friends go on an excursion to visit an archaeological dig near Coba. Jeff, a type A guy who is set to begin medical school in the fall with his girlfriend, Amy; Stacy, Amy's best friend, an irresponsible and promiscuous aspiring social worker whose nickname is "Spacy" along with her boyfriend, Eric, an immature high school teacher; a fun-loving Greek guy nicknamed "Pablo," who lacks a common language with any of the others; and Mathias, an intense, thoughtful German tourist round out the cast of characters.Mathias' brother, Henrich, vanished shortly before the Americans and Greeks met Mathias--he met a beautiful Dutch archaeologist and decided to meet her at her dig, leaving a hastily drawn map for Mathias to follow in case he wanted to join him. Jeff, Stacy, Amy, Eric, and Pablo decide to accompany Mathias in his search for his brother, taking a bus to Coba for the day. Pablo leaves a copy of the map at their hotel for his two companions--who had gone to fish--to find, thinking that they may want to join the group. Things immediately start to go wrong, as the group isn't well prepared for the heat and insects, and the journey becomes creepy. The poorly drawn map leads them to a Mayan village, where the grievously poor inhabitants appear at first disinterested, and then hostile to the foreigners. The Mayans try to force the vacationers to leave the area. Unmoved by the villagers pleas, they find an almost-hidden trail that they follow to the ruins.Gun, rifle, and bow-and-arrow wielding Mayan villagers then will not allow the kids to leave. They are forced to climb a large hill covered in vines and red flowers. The situation turns increasingly disturbing as they find Henrich's corpse, covered in the vine and flowers.Further investigation uncovers numerous other corpses covered in the plant, and the plant, it turns out, secretes an acidic sap which burns them all when it is crushed.A ringing mobile phone at the bottom of the mine under the hill lures Pablo, but the rope breaks as he attempts to retrieve it and he falls, breaking his back. Eric is injured slightly trying to rescue him.Gradually, the group discovers that the vine is sentient and carnivorous, as it begins to lure them to their deaths - one by one - perfectly mimicking the voices of others.Jeff and Mathias amputate Pablo's legs after the plant eats part of them.Amy is the first to go, strangled by the plant whilst Jeff - angry at her for being drunk, ignores her struggles, mistaking for strangled cries for sickness. The plant enters Eric's wound and, though they had removed the bulk of it, Eric insists it's still inside him as he repeatedly cuts himself in an effort to remove it.Jeff is able to hold the group together to a certain extent, always with new ideas about how to conquer their challenges. But, he is ultimately killed by the villagers' arrows while trying to sneak past them. Air-headed and distressed Stacy -- who has held the hope until the last that the other two Greeks will arrive to save them leaves Pablo unattended, and the plant kills and eats him. Eric flays himself alive trying to remove the plant, which has begun to take over his body again, and then accidentally kills Mathias with his knife when Mathias attempts to stop him. With only Eric and Stacy left, Eric begs her to kill him and put him out of his misery, which she ultimately does. Then, she slashes her wrists on the path at the base of the hill as a warning to others, but the plant moves her away, just as it did other warning signs put up by other victims.The Mayans leave.Three days later, Pablo's two Greek friends, with a few Brazilians, climb onto the hill to seek out their traveling companion, bringing several others with them.*THIS IS A SYNOPSIS OF THE BOOK..NOT THE MOVIE.*