'The Flash': Diggle Arrives in Central City in Exclusive "Think Fast" Clip

Warner Bros. Television has provided ComicBook.com with an exclusive sneak peek at tonight's episode of The Flash, titled "Think Fast."

In the episode, The Thinker has infiltrated ARGUS in the hopes of getting control of the last of the bus metas, and Team Flash recruits Arrow's John Diggle (David Ramsey) to try and stop him.

The clip also reveals that ARGUS has been holding Fallout at "The Castle," known to comic book fans as the site of Ted Kord's murder by Maxwell Lord.

The Castle is the headquarters to Checkmate, an organization that is, depending on the writer, either used interchangeably with ARGUS or a competing organization for ARGUS. Checkmate was once the premier intelligence operation in the DC Universe, but ceded that role to ARGUS after its leader, Maxwell Lord, turned out to be evil, and to have compromised all of Checkmate.

During a recent interview, Ramsey revealed that The Thinker will shapeshift into Diggle in an effort to penetrate the secure ARGUS facility where Team Flash is keeping Fallout in the wake of last night's episode.

"You get to see Diggle come in and tear through some ARGUS agents," Ramsey said. "It's always fun to go to Flash because Flash is all light."

Ever since Arrow killed off their version of Amanda Waller in season 4, Diggle's wife Lyla Michaels has been running ARGUS. Until recently, they had not utilized that connection as much as you might think, but after Diggle left Team Arrow, he joined up with ARGUS.

You can check out the official synopsis for "Think Fast," the penultimate episode of the season, below.

When DeVoe assaults an A.R.G.U.S. facility to complete his Enlightenment Machine, Barry (Grant Gustin) realizes the only way he can stop him is if he allows Cisco (Carlos Valdes) and Caitlin (Danielle Panabaker) to accompany him into the facility. Still shaken by Ralph's death, Barry isn't sure he wants to risk any more of his friends' lives and considers taking on DeVoe solo. Viet Nguyen directed the episode written by Sam Chalsen & Kristen Kim.

The Flash airs on Tuesday nights at 8 p.m. ET/PT on The CW. Arrow, on which Ramsey is a regular, airs on Thursdays at 9 p.m. following Supernatural.