Max and the others must rescue Michael after he is arrested for hug; Liz takes a job with a congresswoman who has a hidden agenda.
Brody Davis, the mysterious new curator at the UFO Museum has the group on edge, and Michael and Isabel plotting his demise.
Isabel is deeply moved when Max throws her a surprise birthday party, but she grows troubled after seeing visions of a bound and gagged Tess. Alex does an interesting cop striptease for Isabel. Congresswoman Whitaker is revealed as Nasedo's hugger and as a Skin.
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.
An older Max travels from the future (2014 to be exact) to tell Liz that their relationship will imperil his planet and together they devise a plan to change the future: by making present Max fall out of love with Liz. Not an easy task until Liz tricks Max into believing she slept with Kyle.
After the death of congresswoman Whitaker, Max and the gang visit her hometown, Copper Summit, Arizona, where they find themselves trapped in enemy territory when they learn the whole town population are Skins.
The Skins make all the humans in Roswell, New Mexico disappear turning it into a ghost town. Their assault ends with the death of one of the aliens: Courtney the helpful Skin. Fortunately Tess uses her mindblowing powers and destroys all the other Skins or so it seems until Max and Tess spy a boy resembling Nicholas on a scooter at the end of the episode.
Duplicate versions of Michael, Isabel and Tess come to Roswell after killing their king Zan, to urge Max to attend an important interstellar summit in New York City, but they have their own agenda; Ava stays behind in Roswell.
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 cuddled 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.
When Isabel develops a psychic connection to a girl who has been buried alive, she races to find the teenager before it's too late. Meanwhile the FBI comes to town and starts asking questions concerning Valenti and his involvement with Max and Isabel.
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.
Max tries to stop Alex and Kyle from being buried alive in a cave filled with glowing blue crystals; Isabel is kidnapped by Grant Sorenson possessed by the alien parasite queen; Michael is shot while trying to protect Laurie.
When the gang makes a spur-of-the-moment trip to Las Vegas, in order to spend the DuPree money, the event-filled excursion ends in a faceoff between Max and Michael over leadership; Tess and Liz can't pass for over-21-year-olds; Maria recruits Alex to help her audition for a role that ends up to be for a stripper; Isabel meets a man.
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.
Jim Valenti breaks the news to the aliens and their friends that Alex was killed in a suspicious car accident. Max attempts to revive the already dead Alex, but sadly cannot. The gang must then deal with their overwhelming grief over losing their beloved friend. When the investigation into the car accident leads Valenti and Max to believe that Alex committed suicide by deliberately driving his car into the oncoming path of a truck, Liz blows up and refuses to believe it. Liz begins investigating on her own, finding a photo of Alex and his Swedish girlfriend defaced literally with Alex's head missing. But the weirdest clues are the passage from a Robert Frost poem and the credit card slip that Alex signed just before his death, the strange part: he signed it 11100100100111011001.
A startling breakthrough leads to a renewed connection for two of the gang. Differing reactions to a life shattering event creates tension among the gang, resulting in heartfelt revelations, hidden insecurities and thoughts of leaving Roswell. Meanwhile, Liz enlists Sean in her continuing quest for answers into the death of Alex.
Max is hit with a one-two punch after he discovers that not only is Tess pregnant with his son, but that the baby cannot survive unless they return to their home planet. Liz, Maria and Michael work together to unravel the mysterious double life of Alex. Isabel and Kyle explore her powers as they play pranks on Max and Kyle dreamwalks with a Playmate.
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 hugger that is still out there and threatens the lives of everyone they love.