A freak December heat wave hits the town and sparks romance as Michael's relationship with Maria heats up and Liz's infatuation with Max intensifies; meanwhile Isabel enters into one of Alex's dreams only to discover her likeness already there and dancing with Alex.

Max plays host to actor Jonathan Frakes at the annual UFO Convention while trying to avoid the meddlesome couple who witnessed Max's life-saving abilities on Liz at the Crashdown Cafe.

After Michael has a violent showdown with his father, Max and Isabel's father helps Michael set up his emancipation; the fourth alien emerges as a shapeshifter who watches over Max, Michael and Isabel.

Max witnesses a tragedy and is haunted by the ghost of a man he could have saved, leaving him overwhelmed with guilt and questioning his healing abilities. Isabel aka the Christmas Nazi (dubbed by Michael) tries to brighten up the holiday season and Tess tries to became a part of the Valenti family.

Sheriff Valenti is suspended from the force after refusing to answer the FBI's questions about Max and Isabel, but he soon finds himself right back in the thick of things when Laurie DuPree shows up at his house claiming to be chased by aliens.

Michael and Maria flee from Roswell after helping Laurie DuPree escape from the police, and Max learns that a deadly parasite was released into Earth's atmosphere when their ship crashed 50 years ago.

The onset of junior prom stirs up emotional tumult as Liz tempts fate by asking Max to be her date, Isabel decides Alex is the man she's been searching for, and Michael tells Maria he won't take her to prom.

The sudden death of a close friend shocks the group.

Liz continues her investigation into Alex's death while Isabel plans her future and Maria wonders whether Michael will always be around.

Brody Davis, his mind frazzled from an electric shock,holds several members of the gang hostage, when he begins to remember what happened when he was abducted, such as the New York City interstellar summit and the fact that Max is an alien. Max must use his healing abilities to fix Brody's mind so that he doesn't remember the alien mind that inhabits him. Tess must mindwarp Amy DeLuca into not remembering that Brody held them hostage.

Max, Isabel, Michael and Tess struggle with goodbyes on what they believe to be their last night on Earth before they travel back to their home planet. In the final hours, Max frantically searches for the killer that is still out there and threatens the lives of everyone they love.