Warning: This story contains spoilers from the first part of CWs four-way crossoverInvasion. Read at your own risk. The Dominators have arrived! Credit: Bettina Strauss/The CW In fact, theyre about to be married. We basically pick up with them on the night before their wedding. Alas, Oliver Queens wildest dreams have not come true. Bettina Strauss/The CW These five characters are essentially being held in stasis by the Dominators, Guggenheim says....

Will there be a new Black Canary? Come Wednesday, Team Arrow will have some brand new faces. 502 is very much about reconciling the difference. Credit: Bettina Strauss/The CW To a certain extent, [legacy is] an element of every episode, Guggenheim says. Sometimes thats really overt and in your face, and other times its very subtle. In many ways, its a question of: Can Oliver grow past his past? Oliver thinks every time hes developed or moved forward, he just hasnt been able to....

Who else is returning for the landmark hour? Fortunately, Barry knows a really nice one. It is a love letter to the show, it draws on all previous 99 episodes pretty much. Credit: Diyah Pera/The CW (both) Even the people who we couldnt have, because of conflicting schedules, are represented. At the same time, youve got Flash and Supergirl; thats an enormous amount of fun. Certainly the recruits also play a very large role, an important role, in the episode....

But thats not the only big bad hell be tackling. Were trying to introduce a more adrenaline-fueled flashback story this year, Guggenheim says. Time to expand the Arrow cave! Credit: Bettina Strauss/The CW We planned a normal time jump in broadcast that we typically do. Off-camera, Olivers been officially elected mayor, and hes been operating as mayor. The problem is, hes also been operating as the Green Arrow without a team....

It needed to balance non-Arrowcharacters within its narrative. And it needed to honor the milestone of the shows 100th episode. So how did it do? Credit: Bettina Strauss/The CW It hit a bullseye. Right in the heart. Previously, on theLegends of Flarrowgirlcrossover, the Dominators arrived to Earth. Team Flash assembled the superheroes, including Thea, whofinallysuited up! But Supergirl broke them all free and everybody (save Barry) was beamed up, Scotty....

[Warning: This story contains spoilers from Wednesdays episode ofArrow. Read at your own risk!] Sara is grappling with these really big issues, executive producer Wendy Mericle tells EW. Credit: Cate Cameron/The CW Therefore, Sara is taking herself out of the equation until the lead up toLegends of Tomorrow. Sara is looking for a purpose, Lotz says. Sara is looking for a purpose, and thats what Rip Hunter [Arthur Darvill] offers her....

Thankfully, this episode delivers a jolt of energy that hints at good things to come. John Diggles back in the Army. Thea Queens working as Olivers beleaguered press secretary. Credit: Bettina Strauss/The CW Quentin Lance has crawled into a bottle of booze and stayed there. Felicity… well, Felicitys moved on, too. The season opens with the new SCPD captain hassling Thea over why the mayors late for the police gala....

Diggle, meanwhile, finds himself in a dire situation with no allies at all. The episode opens with Wild Dog and Green Arrow once again in pursuit of the same bad guy. He leaves Wild Dog with a decision … and a card with a date and address on it. Credit: Bettina Strauss/The CW How does he do this? he marvels after he tumbles off. Naturally Oliver strolls in at this moment and shows him howin his business suit....

But overall, this was an important step for the group in its development. Oliver is still upset his success led to the deaths of several innocent men. Basically, his only option is to stick with initiation. Credit: Diyah Pera/The CW This sways Oliver, who decides to put his trust in Bratva. Arrowhas always struggled to tie the flashbacks to whats going on in the present timeline. Renes instincts prove to be true and he tracks down Derek Sampsons base of operation....

And just how drunk do you have to be to get tossed into a Russian jail? Lets recapArrows latest and find out. Anatoly douses him with liquor and kicks him out to pass as a day drunk. Credit: Dean Buscher/The CW With that flashback hair, its an easy task, and Olivers soon tossed into a cell with Friedkin. In conversation, Oliver refers to himself as a once-upon-a-time American whos enjoying everything Russia has to offer....

The bad tonight: Rezoning. We open with some shirtless torture time. Its not the pain that breaks people. Credit: Dean Buscher/The CW Fear of the pain. Of what that pain brings. Of what happens next, Church says. (Im sorry, did I accidentally turn onThe Walking Dead?) Thats cold, Fi. Meanwhile, Theas stuck talking about a rezoning vote to expand low-income housing in Orchid Bay. It needs four-fifths approval from the city council....

Oliver and his team grapple with this question when a new vigilante appears on the scene. Whos to say whos the monster and whos the hero? Good, evil, hero, monster. Credit: Diyah Pera/The CW My friend, truth is a matter of perspective, Kovar says. Oliver responds by stabbing a knife through Kovars hand, then holding another to his neck. He gets the guards to surrender their guns and hustles Kovar toward the exit....

The midseason finale ends on a dark note as Prometheus manipulates Oliver into killing an ally Billie dies! The audience gasps!Arrows midseason finale was twisty and surprising and sad. We open on Evelyn happily handing Prometheus all the intel on Team Arrows identities. Credit: Jack Rowand/The CW Prometheus reminds her hes not going to kill Oliver, hes going to make Oliver wish he were dead. But isnt that how Oliver spends a quarter of his time anyway?...