Arsenal is in front of a house, hoping it belongs to the Boomerang. Oliver is certain it is because it's rigged to blow. Arrows ready and the house explodes upon receiving them. Inside the guys find ARGUS. The man who was killed by the boomerang was an ARGUS agent.
Flashback to Oliver and Amanda Waller. She wants Oliver to talk to some guy to get information. She brought his "tools" which means she wants him to torture him.
At Palmer Technologies, Felicity is greeted by Caitlin and Cisco. They had some vacation days coming. Cisco is friggin' adorable in his desires to see all the toys.
Cisco has so many ideas for improvements.
Diggle is with Lyla at ARGUS. He wants her help. Downstairs the Boomerang is whipping around his weapons with quippy, "what goes around comes around."
Just as Lyla tells 'Johnny' they have it handled, he wonders if they're hearing the "we have it handled alarm."
Oliver and Roy start to suit up. Cisco thinks it's so cool. At ARGUS Diggle pulls out another sweetie, in the hope of getting a gun.
The boys are on their bikes on their way to ARGUS but The Flash is on his way. He blows right by Thea as she's talking with Chase (the DJ).
Just as a boomerang is about to penetrate Arrow, The Flash stops it. Papers fly in his wake. The boy is bad! Arrow shakes his head. He seems unhappy.
Boomerang is Digger Harkness. He's on the Suicide Squad. He escaped during a supposed "sanitization" Lyla approved. His internal bomb must have been compromised.
Back at the Cave, Barry is doing the salmon ladder. Felicity thinks he should have stayed away. The ladder made Barry hungry for sushi and he's off while Cisco hangs helplessly from the ladder. Barry flashes back in and everyone says, "secret identity," but Barry is sure since they're married Diggle told Lyla about Barry. Nope. He keeps secrets for a living. Ah. "My bad," Barry says as he continues eating.
Oliver asks Barry to step back and go away. Starling City is meaner. Barry assures him he's been practicing everything he taught him and he's not going in blind anymore.
Oliver and Barry visit Laurel and Capt. Lance. Oliver wants Lance to help Barry. Laurel pulls Oliver aside to talk about The Arrow being in Central City. He says it's a follow up. Kind of.
The gang is out looking for everyone and Barry tells Roy he likes his outfit. He's still excited as can be.
Arrow catches up to The Flash who has tied up the mob. He had eight seconds to kill. Barry doesn't understand why Arrow is using torture to get information. The air is fizzling out of Barry's balloon of happiness.
Barry and Oliver have words, and this time Barry comes out on top.
Lyla and Oliver share the same words and it seems they both learned them from Amanda. I cannot think of a worse person to learn lessons from.
Flashback to Oliver torturing the guy in Hong Kong. His hands are shaking as he gets ready to strike with his arrow. The dude says inflicting pain is worse than inflicting death. Oliver will figure it out. As he's wondering where the bomb is and not torturing, it explodes in the city behind him.
Diggle and Cisco chat about a world when people didn't kill each other. Roy discovers Barry can walk on water while Cisco decides metahumans were created to stop all of the bad guys from dragging everyone down. His enthusiasm is contagious.
Barry finds a guy, but he has nothing to do with Harkness. He paid him ten grand to give Oliver something. Barry says he's been played.
Felicity gets a phone call on Harkness' phone. A bomerang comes flying and it's too late for them to get out. Lyla starts shooting and the girls hide. Lyla gets a boomerang in the middle of the chest. Luckily Fel and Cait are pretty handy with medical stuff.
Diggle looks to Barry to whoosh Lyla to Starling General.
This causes Oliver to flashback to Hong Kong. Amanda tutors him that reasoning is what's called for in these situations. The men who do these kinds of things aren't those you deal with anything less than extreme measures. Amanda thinks Chang not only has the stomach for this kind of torture, but the talent.
The duo heads to the train tracks to take down Harkness. He laughs at them. He has a contingency in place. Five bombs planted throughout Starling. He doesn't count on The Flash.
The Flash has 90 seconds to transport people to the bombs to stop them. It's a lot of work, but did we doubt they would manage together?
It's longer than 90 seconds. Cisco installed a mini camera on Barry's emblem so he sends a pic to the team. Well into two minutes and counting Barry starts flying the kids to the bombs. It's a good think Barry has an innate GPS system. He does, right?
The kids have to cut their wires exactly on three. They don't explode, so must have done it right. Boomerang isn't all that pleased. He taunts Arrow with weakness. He has some humanity left, but he still pierces Harnkess with an arrow. Barry teases him; he just couldn't resist.
Diggle asks Lyla to marry him when she wakes up.
Caitlin takes the Canary sample. The four young ones bond before Barry and Oliver come in. Digger is now sharing a cell with Slade. The Flash has a pipeline and Oliver has a gorgeous tropical island. With landmines, Felicity reminds them.
Oliver has put in a case with a nekkid mannequin for Barry's suit the next time he's in town. Cisco returns the kindness with a new polymer Kevlar liner that's lighter, allowing him to carry more gear. Felicity wouldn't let him get rid of the hood, for sentimental reasons.
As the groups start to say goodbye, Barry says he and Oliver have some unfinished business.
Oliver flashes back to Hong Kong. Waller is giving him a second chance. A Chinese Triad member working for China White so he can get a stab at redemption. Oh goody.
Oliver and Barry plan on deciding to find out who would best who in a fight. After giving Oliver a pep talk, viewers are left hanging on the results.