New spoilers for "The Flash" Season 7, reveal that Barry Allen and Oliver Queen will swap superhero names. "Arrow" star Stephen Amell posted the first official poster for the new "Arrowverse" crossover, "Elseworlds."

There are also new behind-the-scenes photos for Episode 3, called "The Death of Vibe," and it featured Tom Cavanagh's newest character, Harrison "Sherloque" Wells. The plot of Season 5 will have Barry and Iris West-Allen meeting their daughter, Nora, from the future. Nora stays in the past to learn how to be a better heroine from her father, but they will encounter a new threat, in the form of metahuman hunter, Cicada.

Barry and Oliver switch hero lives

According to Screen Rant, Stephen Amell tweeted the first poster for "Elseworlds," and quickly confirmed that it is not fan art. The poster shows Barry Allen as the Green Arrow and Oliver Queen as The Flash, with the line "Destiny will be Rewritten." The new crossover could be set in an alternate reality, wherein both heroes had different lives, and they are non-canon, just like the Elseworlds DC comics.

The crossover will also feature Supergirl, her cousin Superman, Lois Lane, and Batwoman, as they battle a new enemy, Doctor Destiny, and encounter the mysterious alien named Monitor.

Superman will also sport a black version of his Kryptonian suit.

Sherloque Wells debuts in episode 3

New BTS photos of Episode 3 revealed that Team Flash will meet Harrison "Sherloque" Wells. The photos show Sherloque exploring S.T.A.R. Labs, and meeting each member of the team. The new Wells has been described as a brilliant detective, but his suspicious nature makes him uneasy and untrustworthy to his new teammates.

His skills will be used to find out more about Cicada, and how to stop him. The Harrison Wells character has been a mainstay in "The Flash" TV series, usually being a brilliant scientist.

Tom Cavanagh told Cinema Blend (via Comic Book Movie), that fans can expect a lot from him in the show, and his skills and attitude will have an impact on the team.

"And so this year, we've got a lot of things that we have to solve, and I thought it'd be nice to have a dynamic where we have someone that we don't necessarily know that we can trust, but is undeniably brilliant," Cavanagh said. "Which offers up its own things that you have to contend with when you deal with somebody like that." The episode will also feature the possible demise of Cisco Ramon, after Nora sets him up for a bad plan against Cicada.