On the newest Star Trek: Discovery, Michael joins forces with an enemy to defeat a bigger foe, and the Discovery works on how to fix the network and return home.

Previously on Star Trek: Discovery, Michael met with Emperor Georgiou and was forced to blow her cover to save her own life. At the end, Michael realizes Captain Lorca is actually mirroring Lorca and he tricked the Discovery crew since the beginning.

“What’s Past is Prologue” begins with Lorca freeing his followers from the agony booths they have been tortured in for 1 year and 212 days. One of the people he frees is mirror Landry, the counterpart of the dead security officer from earlier in the season. She suggests getting their people together and regrouping in another place. Lorca says they need to stay on the Emperor’s ship because it is part of his plan.

Lorca and his minions find mirror Stamets, despite his hiding. Mirror Stamets is the one who told Emperor Georgiou about the attempted overthrow. Lorca reveals he got away because of an ion storm which caused a malfunction and he ended up in another universe. He demands mirror Stamets take him to the bioweapon he created for Emperor Georgiou. Lorca then uses the weapon to take out the Emperor’s crew.

Emperor Georgiou is alerted to the situation and Michael warns her Lorca is trying to play with her emotions. She asks to warn Discovery of the danger but is instead Emperor Georgiou sends her to the brig. Michael overpowers the guards and escapes. Emperor Georgiou sends mirror Owosekun to capture Lorca.

Back on the Discovery, Saru’s log plays as a voice over saying the spore drive is working again. Stamets is better, but the mycelial network is not. Stamets is worried a catastrophe is near. They are on their way to the ISS Charon, the Emperor’s ship.

Saru meets with Discovery crew. Airiam noticed the Charon is emitting a large amount of mycelial. Stamets and Tilly explain mirror Stamets uses the network to power the ship by pulling the energy out of the network. The network usually regenerates itself, but mirror Stamets is poisoning the network by using it in this way. It makes the ship powerful but at a great cost. Stamets says if the Terrans are not stopped, the network will fall apart everywhere and destroy the universes.

Lorca addresses Emperor Georgiou over the intercom and paints her as a weakling. He tells the crew to join him in bringing back glory to the empire. He also proclaims Michael must not be harmed. Emperor Georgiou locates Lorca and takes some crew with her to fight. When she gets there, Lorca kills mirror Owosekun and confronts the Emperor. She uses the ship’s defenses to kill some of his people. Once the forcefield is down Lorca’s people start winning. Emperor Georgiou transports herself away and Lorca forces mirror Stamets to disable that feature.

Meanwhile, Michael is in the maintenance ducts, trying to get through to the Discovery. She finally gets through to Saru and tells him that Lorca has been mirror Lorca all along. The crew is shocked at first. Stamets realizes that Lorca was the one that changed the coordinates from his chair to bring them to the mirror universe. Michael tells the crew to leave, to get as far away from the Charon as possible. Saru refuses, and Michael insists Lorca will kill them or take over the Discovery and bring Terrans to their universe.

Stamets tells Michael about the mycelial network is breaking down and if it is destroyed, it will annihilate all worlds. Saru says the Discovery needs to send a proton torpedo to the Charon’s engine. Doing so will destroy the link with the network. Tilly runs simulations and says the orb has a containment field. Michael says she will take care of it and will contact them when she has succeeded.

Lorca and his followers gain access to the throne room and Lorca monologues about fate and threatens to throw mirror Stamets into the mycelial core. Mirror Landry kills him instead and then alerts Lorca to Michael’s transmission to the Discovery.

Photo Cr: Ben Mark Holzberg/CBS © 2017 CBS Interactive. All Rights Reserved.

Lorca broadcasts a video message to Michael, who is stealthy making her way through the ship. He wants Michael to stay with him “in the real world,” says that the Federation will fall, and spouts more prejudiced ideals. He applauds her, saying she is even better than mirror Michael was and continues to offer her a place in his world. Mirror Landry looks for Michael and discovers she outsmarted them and could be anywhere on the ship.

Michael finds Emperor Georgiou and the two talk. Michael swears she wants nothing to do with Lorca and his ideas of fate. The two ponder what they have lost and Michael proclaims she will not lose another Georgiou. The Emperor listens as Michael says she needs to shut down the containment field, and the controls are in the throne room.

Photo Cr: Ben Mark Holzberg/CBS © 2017 CBS Interactive. All Rights Reserved.

Back on Discovery, the engineering crew figures out they cannot destroy the Charon engine without arming their weapons with all of their own spores, leaving them stranded. Tilly runs the simulation and says the blast will incinerate the Discovery. Saru addresses the crew, claiming no one will die today. He shares his belief in the crew and inspires them to find a solution.

Mirror Landry tells Lorca all of Emperor Georgiou’s people have either joined his side or are dead. Michael arrives with Emperor Georgiou, telling Lorca that she will stay with him if he lets the Discovery go. She firmly declares only her mind will be his asset and she is forced to give up her weapon. Emperor Georgiou says she will kill Lorca, and his people laugh.

Photo Cr: Ben Mark Holzberg/CBS © 2017 CBS Interactive. All Rights Reserved.

Tilly thinks they can use the shockwave to power up their spore drive and then Stamets can get them home. The Discovery receives a call from the Charon to leave warp and they answer, believing it is Michael. Lorca addresses them, claiming he did admire the crew and would happily accept any of them into his company if he thought they would disavow the Federation. He tells them they can leave thanks to Michael, and Saru asks to speak to her, realizing now is the moment. Emperor Georgiou and Michael attack Lorca’s followers.

The Discovery fires on the Charon’s engine and it knocks everyone aboard down. Michael and Emperor Georgiou rise and fight Lorca’s people in an epic fight scene. Emperor Georgiou and Lorca take each other on, battling their way around the throne room. Lorca overpowers the Emperor and Michael attacks him, having taken out the rest of his followers. She manages to get a weapon and tells him if he had asked Starfleet for help, they would have tried to get him home. She will not kill him, but Emperor Georgiou has no reservations, plunging a sword into Lorca. He tries to reach out to Michael, who rebuffs him, and the Emperor nudges him into the core and to his death.

Photo Cr: Ben Mark Holzberg/CBS © 2017 CBS Interactive. All Rights Reserved.

Michael takes down the containment area and Georgiou compliments her plan. More of Lorca’s followers arrive and she tells Michael to finish her mission and tries to sacrifice herself to save Michael. While the Discovery gets a lock on Michael's location, she runs and grabs Emperor Georgiou, bringing her along.

As soon as Saru hears Michael is back, he puts the ship on black alert and Stamets gets ready to jump. They fire on the Charon’s core and try to ride the shockwave back to their world. Stamets watches the as the network begins to fix itself, but almost gets lost. He remembers Culber’s words and is able to follow the path to get them home.

The ship leaves the network and all the spores float in the air for a moment in engineering, one landing on Tilly. Stamets tells Tilly to find out if they are in the right place and time. In the transporter room, Georgiou is angry Michael brought her along. Stamets goes to Saru and tells him they are in their own universe, but it is nine months after they left. They try to contact Starfleet but receive no answer. They bring up an updated war map and discover the Klingons won the war.

This was a great episode of Star Trek: Discovery. I cannot sing Michelle Yeoh’s praises enough when it comes to the action scenes. She and Sonequa Martin-Green were so good this episode.  I will be surprised if Jason Isaacs is done with the show as there is no confirmation that Lorca from the prime universe is dead. With only two more episodes left in the first season, I am continually guessing what will happen.

New Star Trek: Discovery episodes are released Sunday’s at 8:30 pm on CBS All Access for the US, and air at 8 pm on Space in Canada. Various countries can use Netflix to watch new episodes on Mondays.