- For the eponymous island, see Lian Yu (Earth-1).
- For other uses of Purgatory, see Purgatory (disambiguation).
- "The name of the island they found me on is Lian Yu. It's Mandarin for purgatory. Now I understand why. The memories, the pain, I've never escaped them. They're always with me, a reminder of what I had to endure with only one thought, one goal-- survive. To save the multiverse, I must become something else. To do that, I have to return to where my journey began-- purgatory."
- —Oliver Queen
|Oliver’s mission takes him to Lian Yu where he tries to ignore the repercussions of the looming Crisis until he receives help from an old friend. Meanwhile, a united Team Arrow faces a recognizable villain.|
Both groups — Team Arrow and Future Team Arrow — have made their way their Lian Yu, where The Monitor wants them to build a Crisis-stopping weapon. Lyla reveals the weapon they're asked to build won't stop the impending crisis; rather it will save the heroes that can stop it. This revelation leads Oliver to unveil his fate to his kids — he's fully expecting to die during the coming days.
Elsewhere, Lyla explains to Diggle that Novu has served as a guardian angel of sorts over the past few years. She says he told her he was the one that rescued her and her unit from an IED when they were stationed in Afghanistan.
Before long, it's revealed Dinah, Roy, and Rene are flying into the island separately. They're a short distance from the island when the plane they're traveling in is hit by a rocket-propelled grenade. The groups split up to find the wreckage and Diggle, Lyla, and Connor eventually come across Dinah and a severely injured Rene — Roy is nowhere to be found. They eventually find him pinned underneath a piece of airplane wreckage, with his arm completely crushed. Connor tries recommending an amputation, though his father instantly disagrees.
Oliver and Laurel come across the device Dinah and her plane team was carrying but they run into an obstacle — people Oliver previously encountered on the island, who have since passed on, have seemingly returned in physical form. This includes some Deathstroke-associated mercenaries led by Edward Fyers and Yao Fei.
Laurel escapes after Oliver and Yao Fei chase after the mercenaries. After Laurel syncs up with Dinah, Diggle, Connor, and Roy, the latter convinces the group to amputate his arm so they can help Oliver out. In their pursuit, Oliver and Yao Fei get entrapped in nets strung by trees, something that only momentarily hangs them back. Yao Fei uses a lens and his knife to burn out of the nets, allowing Oliver to rendezvous with the rest of the group at camp — where they've been surrounded by Fyers and his men.
An all-out battle breaks out between Team Arrow and Fyers' men. Oliver and William begin powering up the device when it's revealed Oliver isn't the one that powers it — Novu made it so Lyla would be the wielder of the world-saving device. Lyla turns it on and it instantly disperses of Fyers and all of his men. The second after she uses it, she then steps through a portal, presumably to reconnect with Novu ahead of the Crisis.
As everyone begins to disperse, Oliver and Diggle have a heart to heart. During this, Oliver asks Diggle to track down Felicity after Crisis and have her reconnect William and Mia so they don't have to grow up apart. They two then agree the future version of the characters need to be returned to 2040 before Crisis begins.
Oliver's speaking with Mia to end the episode when the skies turn red and a lightning storm begins. Lyla arrives and tells the pair she's been renamed Harbinger and the Crisis has begun.
- Stephen Amell as Oliver Queen/Green Arrow
- David Ramsey as John Diggle/Spartan
- Rick Gonzalez as Rene Ramirez/Wild Dog
- Juliana Harkavy as Dinah Drake/Black Canary
- Katherine McNamara as Mia Smoak/Blackstar
- Ben Lewis as Older William Clayton
- Joseph David-Jones as Connor Hawke
Special appearance by
Special guest star
- Audrey Marie Anderson as Lyla Michaels/Harbinger
- Byron Mann as Yao Fei Gulong
- Sebastian Dunn as Edward Fyers
- Tom Cavanagh as Harrison Nash Wells
- Jeffrey Robinson as Billy Wintergreen
- LaMonica Garrett as Mobius/Anti-Monitor (voice)
Preparation ran from September 10 until September 18, 2019. Shooting ran from September 19 until October 1, 2019.
- The title references the English translation for Lian Yu.
- This marks the first appearance of Edward Fyers since the Season 1 finale, "", and his only appearance in the present day.
- Billy Wintergreen also appears for the first time since "" and this marks his only appearance in the present day.
- This is the first appearance of Yao Fei Gulong in the present day; having previously appeared in Season 1 through flashbacks and in "" as a vision in a flashback.
- Interestingly enough, Yao Fei wears his green hood and and his Carbon fiber longbow, both of which he gave to Oliver, instead his army outfit he wore before his death.
- Like "", this episode doesn't have many callbacks to previous seasons, mostly from the Season 1 flashbacks on Lian Yu.
- Like in the comics, Roy loses his arm.
- This is the last episode of Arrow to centrally take place on Earth-1.
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