Tess's book suggests that she and Max are predetermined mates, as are Michael and Isabel, who thinks she might be pregnant -- with Michael's baby. Meanwhile, Nasedo disguises himself as Max and kidnaps Liz as part of a plan to trap FBI agent Pierce.

After escaping from Pierce, the aliens save Nasedo. Michael accidentally kills Pierce. Nasedo, as the aliens' guardian takes Pierce's place to help the aliens. The aliens figure out how to use the devices and release a message from Max and Isabel's real mother. She says Max is their leader and Tess, his fiance and that Michael is Second in command and he is Isabel's fiance. After hearing all this Liz runs out.

Michael discovers the hidden history behind the 1947 crash when interviewing a World War II survivor for a school project. The story unfolds with familiar faces portraying people in 1947.

Max and Tess depart for the interstellar summit in New York City with Rath and Lonnie, Michael and Isabel's duplicates, who both harbor a secret agenda for their future king and an alliance with Nicholas, the Skin. Ava reveals to Liz that Rath & Lonnie murdered Zan. Tess is kidnapped by the dupes after Max learns of their true intentions. When Max finally finds Tess she reveals that they tried to read her mind to find the Granolith but she resisted. She then says that they're gone but did they die or are they still out there? Ava says goodbye to Liz and leaves Roswell.

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.

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.

With Alex's ghost as her guide, Isabel must finally confront her fears about love and her conflicted feelings for Jesse. Meanwhile, Maria happily discovers a whole new, human part of Michael in, of all places, a bowling alley, and Liz and Max struggle to remain together despite her father's insistent disapproval.

When an old love visits Maria her passion for music resurfaces, which jeopardizes her relationship with Michael. Meanwhile, while Max's father is still trying to put together all the pieces of his investigation, Isabel joins Max in the quest to stop him.

When Max is fascinated by an intriguing autistic child he wonders if his own lost child is attempting to reach out to him. Meanwhile, Michael plays Santa to Maria and Liz's elves at a charity event. Isabel and Jesse share their first holiday together as husband and wife.

When a journalist friend of Jesse's comes to Roswell, Isabel discovers he's investigating her, Max and Michael, after he witnesses Michael using his powers. Meanwhile, Isabel fantasizes about what her life would be like if Jesse knew her alien secret through the device of a 1960s sitcom a la "Bewitched."

Michael witnesses a fatal crash between a fighter jet and an alien vessel, and embarks on his own investigation leading to the recovery of an artifact. Meanwhile, Isabel spends the day with her mother, who's harboring a secret agenda and is working with her husband to discover Max & Isabel's secret, which leads to a shocking revelation.