I Am Legend focuses on Lieutenant Colonel Robert Neville (Will Smith), a doctor fighting a virus that has seemingly wiped out all of the human race except him. A virus was created using the measles in order to cure cancer. Three years after successful human trials were conducted we see that New York City is being reclaimed by nature, with grass growing through the streets, herds of deer and lions roaming free. There is also virus-infected-humans lurking. They cannot come out during the day because the sun burns them to death if exposed for too long, but in the night they ravage the city.
Robert methodically makes his way through his days with his companion, Sam (Samantha), his female German Shepherd. He has complete immunity to the virus and Sam is immune to the airborne virus, but can still be infected if bitten. Robert’s routine consists of working out, hunting for food, he goes to the dvd store where he watches movies in alphabetical order, and he has set up mannequins as customers and employees whom he’s given names, and with whom he speaks. He clears buildings for supplies and at midday when the sun is the highest in the sky he is always at the South Street Seaport waiting for any survivors to show up who have heard his radio message broadcast on all AM frequencies that he can provide, food, shelter and protection. Most importantly, Robert continues to conduct experiments on infected animals (we see rats in his laboratory), as well as infected humans, all of which have died in his experiments, but his most recent serum has proven to be effective in one rat, returning it to a lower state of aggression and proper pigmentation has returned.
The infected hosts have an increased body temperature of 106° Fahrenheit, their skin loses pigment, they have an increased heart rate. They, then only roam during the night and live in darkness. Their aggression is off the charts and they are able to sniff out human flesh. Their hearing is enhanced and they always attack any noise that is made with a bloodthirsty rage. There is no communicating with them as all reasoning appears to have gone.
We learn that New York City was ground zero for this virus, and the military quarantined the city by bombing the bridges, leaving behind the infected. Robert’s wife and daughter have been killed while aboard a helicopter escaping the city. A mid-air collision with another helicopter spinning out of control claimed their lives, and he has dedicated his life to finding the cure.
While hunting in the streets of NYC, Sam chases a deer into a dark building. Robert goes after her and encounters a group of infected humans. They both narrowly escape the building, and since it is day the infected cannot chase them into the light.
Robert set a trap to catch an infected human in order to conduct his experiment with the new serum that has shown promising results. He catches a young female (18-20 years old), and after knocking her unconscious, an infected male runs to the doorway between the darkness and light, screaming in rage. We can see that there is a connection between him and the female Robert has captured.
Robert is able to get her back to the laboratory safely and his initial injection of the serum causes her to flatline. He injects her one more time and she comes back to life. He secures her in a glass cell to keep watch over her.
Once daylight returns, Robert returns to the streets to discover one of his mannequins from the dvd store has moved, many blocks away from where the store was located. He begins to lose control and, not knowing whether the mannequin is real or not, he shoots it. We see that his extreme isolation has taken its toll on his psyche. When he goes to check the mannequin, a similar snare trap that he set to capture the infected female earlier has been set in the puddle where the mannequin is, and he is strung up by one leg. Robert hits his head on the pavement on his way up, and is knocked out for hours. He wakes up to his watch alarm warning that the sun is setting, and Sam is barking, seemingly trying her best to wake him up. He is able to cut himself down with his tactical knife, but when he hits the ground the knife punctures his right thigh, and he can only crawl back to his SUV. As the sun continues to set, we see the infected male from earlier with three infected dogs. He releases them, but they have to wait for the sun to go behind the buildings in order to attack Robert and Sam. Once it does, they sprint for them and Sam pounces on one as Robert makes it to the SUV, pulling a pistol from the driver side door he is able to kill the dog, a third dog attacks him as Sam continues to struggle with the other. By the end of the attack all infected dogs are dead, Robert is okay, but Sam has been severely bitten and cannot walk.
Robert takes her back to his lab and injects her with the serum in hopes that it will stop her from turning. He cradles her in his arms and waits. Her eyes and gumlines begin to change and she becomes violent towards him, trying to take bites out of his flesh. He has to do the unthinkable and her kill her with his bare hands. This loss is monumental for Robert, and he goes back out, this time at night to the Seaport with a deathwish trying to kill as many of the infected as possible, but they overrun him and topple his SUV, and just as they are about to make a meal out of him bright lights appear from nowhere, and they simulate sunlight, burning off the infected.
Robert is able to tell his unseen rescuers where his home is. They get him there and he passes out. In the morning we discover that Anna, and a young boy named Ethan have rescued him. They are on their way to Vermont to a survivor’s colony. They heard Robert’s message on the AM radio the same day Sam was killed and waited there for him all day. They want Robert to come with them, but he will not go. He is dedicated to curing this virus in New York, ground zero. This is the promise he made to his wife and daughter.
Robert also cannot believe that there is anyone else that is alive, or that there is a survivor’s colony, and when he asks how she knows it’s there, she tells him God told her. She tells him that if you listen in the silence God will speak, it is how she knows there is a survivor’s colony, and the reason why she turned the radio on and found him. This sets him off and he proclaims that there is no God who would do this to people.
He goes back to the laboratory in the basement to work, and when nightfall comes the house is under attack. The infected had followed them back to his home when he was passed out the night before, and they are there to kill them and get the female back that he is running experiments on.
Robert sets off explosives he’s rigged outside his home killing a large amount of them, but the onslaught continues and they get into the house. Robert is able to fight off enough of them and get himself, Anna and Ethan to the basement where they secure themselves in the same glass cell as the infected female. He sees that the female is getting better, she looks human again. As he’s seeing this the infected male has come to get the female back and is slamming so hard into the glass that it is cracking. Over and over he violently slams his body into the glass. As this is happening the film goes silent as Robert is having a flashback to his daughter on their car ride to the helicopter before her death. She says, “Look daddy a butterfly.”
We see that the infected male is stepping back for another run at the door, but when he does the crack resembles wings. Robert turns towards Anna and Ethan to see a tattoo on Anna’s neck of a butterfly. A moment of clarity that is so rare in life. He knows exactly what to do.
Robert extracts blood from the female who is healing and gives it to Anna telling her to take to the colony. It’s the cure for the virus. He places them in the crawlspace behind them, but won’t get in with them. “They won’t stop,” he says. When she asks what he’s doing he says, “Listening.” He closes them into the crawlspace and finds a picture of his wife and daughter. Then he takes a grenade, pulls the pin and sprints straight towards the the glass door the infected male is charging at, they crash into each other, and the grenade detonates.
We find Anna and Ethan driving in the daylight. They are safe. They stop at a large gate in the middle of a country road and get out. The gate opens. They’ve found the colony. It’s real and they have the cure Robert gave his life for only hours prior.
