Zod and his soldiers release a virus into the air that turns humans into zombies. The only way to stop it is to make an antidote from the blood of another Kryptonian. After Lois is infected, Chloe pleads with Clark to donate his blood to stop the epidemic, even though it risks outing him to Zod.
original airdate--October 9,2009 rating--2.30 million
song--Theme song--"Save Me" by Remy Zero
- "One Moment More" by Mindy Smith
- "Hate Fueled Man" by Brian Tichy / MasterSource
Trivia: Jody Thompson appears as a police officer who makes out with Oliver. She also appeared as Gia in Season Five's Fade, where she kissed Clark.
- This is the second episode of the season in which all main cast members appear, which is rare for Smallville in recent years.
- Lois's outfit is similar to Jill Valentine's outfit in Resident Evil 3. Mainly the blue top and the black knee high boots.
- At the beginning of the episode, Clark wakes up and finds Metropolis deserted. This bears a strong resemblance to the first scene of the film 28 Days Later. The appearance and behavior of the virus-infected zombies is also very similar to the "Rage"-infected zombies from the same film. The opening sequence is also similar to the ending sequence from the film Resident Evil.
- At about 20 minutes into the show, Chloe Sullivan displays an aerial photo of Metropolis on a computer monitor. The aerial photo is actually of the south side of Chicago Illinois.