SPOILER ALERT: Do not read if you have not yet watched “Elseworlds, Part 1,” the first part of the 2018 “Arrowverse” crossover, which aired Dec. 9.

After past crossovers that introduced beloved characters’ doppelgangers, a wedding and death, “Elseworlds,” the fifth annual “Arrowverse” event, had a lot to which to live up. Unlike previous years, this crossover actually went smaller in scope, featuring only three of the four shared universe DC on the CW series: “The Flash,” “Arrow” and “Supergirl.” However, emotionally, the goal was to go deeper, says “Arrow” showrunner Beth Schwartz.

“Elseworlds, Part 1” delivered on that right from the start, with a look at a decimated Earth-90 — a landscape of destruction that included numerous dead villains and 1990s-era Flash (John Wesley Shipp) standing face-to-face with The Monitor (LaMonica Garrett), who threw out a few threats before Flash had a chance to speed off.

The next time the Monitor was seen was on Earth-1, visiting Dr. John Deegan (Jeremy Davies) moments after he has been laughed out of a conference. The Montior gave Deegan a book he had been using on Earth-90, telling him he can shape reality with it however he sees fit.

Popular on Variety

After this quick setup, the first episode of the crossover dove right into the big hook of “Elseworlds”: a power-swapping experience for Barry Allen (Grant Gustin) and Oliver Queen (Stephen Amell). Oliver woke up in Barry and Iris’ (Candice Patton) apartment, greeted with pancakes and a kiss from Barry’s wife. Soon enough Cisco (Carlos Valdes) called with information about a Central City warehouse crime, to which Oliver headed over quickly but not without some issues adjusting to Barry’s skill set.

At the warehouse, Oliver struggled to get the hang of super speed and threw an out of control lightning bolt to dispatch the criminals. As he zoomed off he missed that the same bolt of lightning and also activated the Amazo android, which was a nice Easter egg for comic book readers and longtime viewers alike who previously knew Amazo as the boat featured in “Arrow’s” second season.

Meanwhile, Barry wasn’t having a much better time of things: He “awakened” in the middle of a sparring match with Diggle (David Ramsey). He didn’t have his speed, and although he had Oliver’s arsenal, he didn’t quite have the immediate knowledge of how to best use the tools at his disposal, struggling to use the right arrow in a quiver full of them when trying to take out some criminals. Luckily, Oliver showed up at just the right moment and sped Barry off to figure out what was going on.

Team Flash — despite being much warmer than Team Arrow at times — couldn’t quite wrap their heads around Oliver and Barry’s affliction, but Barry believed if they could get Iris on their side they could convince the others, so he coached Oliver on how to talk to his wife. Oliver thought it was too flowery but tried anyway. Unfortunately, the team came to their own conclusion that something else was wrong and knocked the two superheroes out, holding them in the pipeline while they tried to work on a solution.

While Oliver and Barry worked with each other on their skills to help them break out of the pipeline — with Oliver showing Barry how to dislocate his thumbs and Barry talking Oliver through phasing — Cisco vibed the Monitor, who came with a clear warning: Give up.

Oliver and Barry successfully broke out of their prison and decided to enlist Supergirl’s (Melissa Benoist) help in figuring out if the weirdness of their situation was contained to their Earth. Before they could head off, Iris intercepted them, allowing the real Barry a chance to talk to his wife and tell her that no matter what mask he’s wearing, she’ll always be able to see through it. This is just what she needed to be convinced who her real husband was, and she let them head to Earth-38.

Enter Kent Farm. Or more literally, Barry, Oliver and Kara (Benoist) visited Kent Farm and her cousin Superman (Tyler Hoechlin). This was also a chance for the show to first introduce the “Arrowverse’s” Lois Lane (Bitsie Tulloch). She and Superman had been off in Argo City, so Kara was catching them up on what was happening in National City when Barry and Oliver bursted into their world. Kara immediately recognized them as who they really were and was just as shocked to see their powers had been swapped. Notably, this was the first time the Emerald Archer and Scarlett Speedster met Superman in the “Arrowverse.” Barry was characteristically excited about it, while Oliver tried to puff his chest out a bit more.

As Barry and Oliver wound down on Kent Farm, they continued to teach each other about their powers. Barry wanted to see if he could hit Oliver with an arrow while Oliver was speeding at him. They gave it a try, but Oliver caught the arrow. Then, in a sequence that mirrored a training session between the two during the first “Arrowverse” crossover, Barry hid crossbows in the ground that shot Oliver in the back as he ran.

Naturally, this set Oliver off, and he tore into Barry for joking around while he was trying to figure everything out. The two stormed away from each other, leaving the others watching them. But it was a short-lived burst of anger, with Oliver soon explaining he was so used to channeling his darkness and the bad things that happened to him while fighting that it pissed him off when Barry did things differently. The two realized that they have been the most successful at channeling each others’ abilities when they emulated each other — Oliver was able to phase because he was laughing and having a good time, while Barry was sharp with the bow and arrow when he got angry at Oliver.

Of course, they figured this out just in the nick of time, too. Cisco vibed to them and explained that while they were away, the Amazo android was wreaking havoc on Central City. The android could absorb the ability of any meta it scanned, and it already took on a couple. So the duo headed back to their Earth with Superman and Supergirl tagging along for a four-on-one-fight between superheroes and android.

Soon enough Amazo absorbed all of their powers, which forced Barry and Oliver to focus on channeling one another. Oliver led Amazo on a wild chase through the city while the others set a trap. And right before Barry shot the fatal arrow, he got to whisper Oliver’s favorite phrase: “You have failed this city.”

After the Amazo debacle was dealt with, Team Flash was more convinced about Barry and Oliver’s dilemma. Cisco mentioned his vibe, and they took another look at the moment, this time seeing the Monitor giving Deegan the book — but Monitor also saw them and uttered another warning. Oliver made a super-speed sketch of what they saw and pointed to Wayne Tower in the background.

That’s right, they’re off to Gotham City in “Elseworlds: Part 2.”