Why Wally West Is Gone for Most of "Crisis on Earth-X"

The Arrowverse united tonight for the first installment "Crisis on Earth-X" crossover, but one hero has a good reason for missing most of the proceedings.

Spoilers for the first hour of "Crisis on Earth-X" below!

Tonight's episode followed the day leading up to the wedding of Barry Allen/The Flash (Grant Gustin) and Iris West (Candice Patton). After being absent from The Flash for several weeks -- and apparently battling a giant starfish in the process -- Wally West/Kid Flash (Keiynan Lonsdale) returned, just in time for the wedding.

Wally was shown periodically throughout the episode, largely in the awesome fight sequence between the wedding guests and the invaders from Earth-X. Once the Earth-X villains left, the Arrowverse's heroes regrouped at S.T.A.R. Labs, trying to decide what to do next.

Barry decided that since the Earth-X villains know their real identities, they need to keep as many of their loved ones hidden away and safe as possible. Barry requested that Wally take Joe (Jesse L. Martin) and Cecile (Danielle Nicolet) away to safety. Wally protests, saying that he should be helping by fighting alongside everyone else. Barry tells Wally that he is helping, and Wally ultimately agrees to leave.

This might disappoint some The Flash fans, considering Wally's desire to be a part of last year's "Invasion!" crossover and his lack of screentime thus far this season. But who knows? Maybe Wally could partner up with some of his Arrowverse buddies in the future -- potentially as a member of the Legends of Tomorrow.

"Crisis on Earth-X" is a four-hour event that will air on November 27th and 28th beginning at 8 p.m. and running for two hours each day; Supergirl (8 p.m. Monday), The Flash (8 p.m. Tuesday) and Legends of Tomorrow (9 p.m. Tuesday) will remain in their normal time slots but Arrow will move from Thursday to a 9 p.m. Monday placement for the week.