Dominators' alternate reality

An alternate reality was a computer-simulated reality created by the Dominators during their attack. It housed a seemingly perfect world using certain events/memories from the lives of Sara Lance, Oliver Queen, Typhuss James Kira, John Diggle, Ray Palmer, and Thea Queen when the Dominators kidnapped them.

The reality was used by the Dominators to study the heroes' minds and determine their weaknesses in preparation for and as a distraction from their invasion of Earth.

History
Oliver Queen jogs through the forest surrounding the Queen Mansion one morning. Afterwards, he showers with his fiancée, Laurel Lance, and they prepare to get dressed for their rehearsal dinner tonight.

Thea gives Oliver a hōzen as a pre-wedding gift. Robert and Moira then arrive. As Oliver and Robert prepare to leave for an appointment with the tuxedo tailors, Moira reflects on how much her children have grown. A maid comes in and almost drops a vase, but Oliver instinctively catches it, much to his confusion.

That night, Sara arrives to stay at the mansion for the wedding. After Laurel helps take out her luggage, Sara admires her sister's new necklace. Laurel explains the emblem is a canary, triggering a sudden reaction from Sara. Laurel is concerned but Sara shrugs it off and hugs her sister, saying she missed her.

As Robert and Oliver head home from the tuxedo shop, Robert reminds his son that he will be sworn in as mayor in less than two months and can't train a replacement as CEO of Queen Consolidated in that time. Oliver suggests Walter Steele, but Robert explains the board of directors won't back him. He insists Oliver become CEO since the company should stay in the family, but Oliver wants to make a name for himself. Robert warns that the board will accept Ray Palmer's buyout offer if Oliver doesn't take the position. As they talk, Oliver glances at a nearby building, Smoak Technologies, and gets an odd sensation. Suddenly, a mugger draws a gun on them, demanding their valuables. Oliver unexpectedly steps in front of his father. Before he can do anything, The Hood drops down from the rooftops, takes out the mugger, and leaves.

Back at the mansion, Robert tells Thea what happened and they agree to keep Moira in the dark for the time bing. As Robert compliments his son for trying to protect him, Oliver experiences flashes of the real world, including the sinking of the Queen's Gambit and Robert killing himself. When Laurel arrives to check up on him, Oliver has a vision of her near-death in a hospital gown. A troubled Oliver goes out to get some air and says he'll meet Laurel later at their rehearsal dinner.

Oliver heads to the SCIS precinct and approaches Quentin. Quentin explains Lucas Hilton told him what happened and assures Oliver that they captured the mugger thanks to the vigilante. Oliver remembers more of his crusade as The Hood from the real world as Quentin urges him not worry about the vigilante on the night before his wedding. Oliver claims he is just a little shaken up and will meet Quentin at the restaurant. Before Quentin leaves, he commends Oliver on growing into a remarkable man since his teenage years, one whom he's proud to have as his son-in-law. Oliver stares at a map for the city and flashes to the spot where the Arrowcave is located.

At the restaurant, Sara assures Laurel that Oliver will come to the rehearsal dinner. Laurel isn't convinced, citing his recent odd behavior, but Sara believes it's normal. Ray is at the restaurant and comes over to offer his congratulations to Laurel. When Laurel introduces him to her sister, Sara gets flashes of her and Ray's time together in the Legends. Ray appears confused as well and wonders if they have met before. After a moment's hesitation, Sara denies it. As she and Laurel leave, Ray stares after her, slightly suspicious.

Oliver arrives at his abandoned campaign office and takes the elevator down to the Arrowcave. Felicity Smoak is working at a computer station and is shocked to see him. She yells to someone that they have an unauthorized entry and the Hood drops down. Oliver manages to catch his first blow, but the vigilante easily knocks him out.

When Oliver wakes up, the Hood asks how he found the place. He demands Oliver leave, as no one can know his secret. Oliver recognizes his voice as John Diggle, flashing to their friendship in the real world, and reveals his identity. Despite Felicity's protests, Diggle removes his hood. Oliver realizes that Diggle used to be his bodyguard, but the latter believes Oliver must be talking about his brother Andy, who works in personal security. Oliver states Diggle was in the military, which the latter confirms, explaining he wants to atone for some questionable acts during his service. When Felicity tries to urge Diggle to stop giving away this information to a stranger, Oliver has flashes of meeting and falling in love with Felicity in the real world. He deduces Felicity's identity as well, throwing her off. Oliver insists the situation isn't right, saying Diggle isn't supposed to be the vigilante and actually killed Andy. Angered, Diggle slams Oliver to the floor and tells him simply he's having a psychotic break. He shoves Oliver into the elevator, ordering the latter to return to his life, saying that he's got "everything" and shouldn't throw it away.

The next day, Moira helps Thea put on her bridesmaid dress. Thea assures her mother that she's never been happier and they hug. Suddenly, Thea remembers watching Moira's murder and pulls away, shocked. Moira asks if she's okay, to which Thea quickly replies that she's fine.

Sara is helping Laurel put on her wedding dress when Oliver arrives, wanting to talk to Laurel in private. Laurel and Sara are angry that he skipped the rehearsal dinner but Sara eventually agrees to give them a minute alone. When Laurel wonders where he was last night, Oliver simply affirms he wants to marry her as soon as possible and suggests that they elope. He repeats what Diggle said about him having "everything", and worries that he'll give it up. Laurel reminds Oliver that over 200 guests are coming and his parents paid a lot of money for their wedding. Oliver apologizes for his abruptness, stating that the only thing which makes sense right now is that he loves her. Oliver vows to become CEO of Queen Consolidated and work hard to be deserving of Laurel's love, much to her joy. Diggle then arrives, having been let inside by Raisa, and asks if he and Oliver can talk.

Diggle, Typhuss and Oliver go out to the gardens, where Diggle asks Oliver if he also felt strange when seeing Smoak Technologies, as if it didn't belong. Felicity said that she never owned a building or company, and they started having memory flashes upon seeing it. Diggle tried to draw one of the memory flashes and shows Oliver his sketch of a Dominator. Oliver, Typhuss and Diggle begin to realize their situation is fake, a world where Oliver never got onto the Queen's Gambit or became a hero. Oliver warns Diggle that their captors are going to push back. Deathstroke then steps out of the trees, sword drawn, and attacks them. He manages to take them both down, but Sara arrives, disarms Deathstroke, and runs him through with his own sword. She then expresses shock on how she did that.

The trio head inside the mansion, where Diggle, Typhuss and Oliver explain they've been experiencing a shared hallucination. Oliver reveals that Sara learned her fighting skills in a place called Nanda Parbat. Sara is incredulous, but Oliver has her think back to the last thing she remembers before arriving at the mansion last night. She remembers their fight against the Dominators in the real world and six of them being teleported away. Sara confirms the other two were Ray and Thea. Diggle figures that the reason Smoak Technologies seems so out of place is because it's the key to them escaping their shared hallucination.

At the pre-wedding party, Malcolm Merlyn and Thea talk about Tommy being a doctor in Chicago and Thea running Verdant. Sara finds Ray, who introduces her to his fiancée, Felicity. Pulling him aside, Sara prods Ray into thinking about their real lives. Ray remembers that his fiancée was Anna Loring, not Felicity. Meanwhile, Oliver arrives, looking for Thea. Robert and Moira approach Oliver, concerned about his unstable behavior. They insist that marrying Laurel and leading Queen Consolidated is his life now, but Oliver says it's not. He tearfully hugs his parents goodbye, apologizing.

Oliver finds Thea and Sara, only to learn that his sister refuses to leave, insisting that this reality better than their real lives since Oliver's parents are alive. Oliver sadly states that he wants them to be their parents, but they're not. Oliver sends Sara to wait with Diggle, Typhuss and Ray outside. He points out to Thea that they can't stay here, as they have responsibilities and people who count on them in the real world. Thea figures there are now actual superheroes to handle those matters, believing she and Oliver can be happy here. Thea suggests that this world could be Oliver's reward for all of the sacrifices he's made, but Oliver explains he didn't make those sacrifices for a reward and there's so much more left to do. He begs Thea to come with him because he can't do it without her, but Thea can't bear to lose her family again. Although saddened, Oliver accepts her decision. He hugs and wishes his sister well before leaving.

Oliver meets Sara, Diggle, Typhuss and Ray outside and informs them that Thea is staying. He figures that the Dominators built in safeguards; manifestations from their memories designed to keep them there. Just then, an arrow is shot at Oliver by Malcolm. Malcolm, Deathstroke, Damien Darhk, a Ghost, and a member of Slade Wilson's army arrive to block their escape. Thea then joins the battle, remembering how she can't lose her family again. The two sides clash, with Thea battling Malcolm, Sara attacking Darhk, Oliver taking on Deathstroke, Diggle and Typhuss fighting the Ghost, and Ray going after the Mirakuru soldier. Diggle and Typhuss defeats the Ghost, but John is wounded by a bullet. Ray is forced to grab a gun and kill Slade's soldier. Thea and Sara take out Malcolm and Darhk, respectively, with arrows. Thea tosses Malcolm's bow to Oliver, who uses it to shoot an arrow into Deathstroke's eye, killing him.

Laurel then arrives outside, asking Oliver and Sara about what's going on. Sara simply explains they have to go. Laurel protests, insisting they can fix whatever's wrong, but Sara says they can't. She sadly embraces her sister, admitting that "some things you just can't fix", before leaving in tears. Oliver then apologizes to Laurel, admitting he isn't the person she fell in love with and she always deserved better. Oliver kisses Laurel's forehead, affirming that he loves her before walking off.

The six heroes arrive at Smoak Technologies and find a glowing portal. As the others head inside, Oliver receives visions of Moira, Felicity, Tommy, Roy Harper, and Laurel expressing how he is a hero. A vision of Robert then reminds Oliver that saving Star City is his responsibility now. Oliver nods to them and enters the portal, returning to the real world.

Changes to the reality

 * Robert Queen, Oliver Queen, and Sara Lance never boarded the Queen's Gambit.
 * Robert and Moira Queen, Tommy Merlyn, Andy Diggle, and Lucas Hilton are alive.
 * Felicity Smoak and Ray Palmer are engaged.
 * Typhuss and Samantha Carter are engaged and about to be married.
 * Oliver and Laurel are engaged and about to be married.
 * Oliver never cheated on Laurel with Sara and Samantha Clayton.
 * Quentin Lance is still an SCIS detective.
 * Laurel and Quentin never became alcoholics.
 * Tommy works as a doctor in Chicago.
 * Malcolm Merlyn is still the CEO of Merlyn Global Group and has a good relationship with Tommy and the Queen family.
 * Thea Queen (presumably) does not know that Malcolm is her father.
 * John Diggle is the Green Arrow and Felicity is the only other member of his team.
 * Robert has just been elected Mayor of Star City.