Sure enough, it's revealed that Ruth is actually a vampire and was sent to spy on Robert after he killed her husband.

Her ability to walk around in the sun seems like clear-cut evidence that she's not a vampire, but he becomes suspicious of her aversion to garlic and her unconvincing story about how she's survived all this time. As in the movie version of I Am Legend, there's a pivotal moment in the book where Robert meets a woman who appears to be another human survivor, Ruth. They retain all their intelligence and can still talk, coming out at night to taunt Robert outside his house and tempt him to leave. They are also, besides their pale skin, very difficult to distinguish from regular humans.

Yes, in the book version of I Am Legend the hemocytes are explicitly labelled vampires and come packaged with many vampiric traits, including not only a deathly aversion to light but also a fear of garlic and religious iconography. In the book, ' I am legend' are the final words that Robert thinks on his deathbed, as he realizes that in death he will become a terrifying legend just like vampires once were. In fact, without the original ending, the movie's title of I Am Legend doesn't actually make much sense. The original ending, however, is much more in line with what happens in the I Am Legend novel. It was replaced in I Am Legend's theatrical cut with a more traditional Hollywood ending, where the hemocytes remain mindless savage zombies and Robert dies a hero after discovering a cure for the virus. The ending did not go down well with test audiences, who were unhappy with the implication that the hero of the movie was actually a villainous figure. Related: Why I Am Legend Is NOT A Zombie Movie

Looking at the wall of photographs of his past experiment subjects, Robert understands that he is the monster in the eyes of the hemocytes: a predator who has been capturing and torturing them. He realizes that the leader only wants the return of his mate, and that the hemocytes - whom Robert believed incapable of higher brain function - can experience attachment, love, and even restrain themselves from committing violence. When the leader makes the symbol of a butterfly on the reinforced glass, Robert connects it to the butterfly tattoo on the female hemocyte he's been experimenting on. In the original ending for I Am Legend, Robert is cornered in his basement laboratory along with fellow survivors Anna (Alice Braga) and Ethan (Charlie Tahan), with the hemocytes having broken into the house.

I am legend book cover