SPOILERS for Star Trek: Discovery, "Vaulting Ambition," follow.
Fans of classic Star Trek have felt like something is off with Star Trek: Discovery. In particular, they've questioned the behavior of Gabriel Lorca as captain of the USS Discovery. Fans felt that Lorca was not behaving like a true Starfleet captain. It turns out that's because he isn't a true Starfleet captain. He's an officer of the Terran Empire.
The reveal came after a long conversation between Michael Burnham and Emperor Georgiou. Georgiou at first promises Burnham that everything will be as it was and reveals that she raised Mirror Burnham as her own daughter. However, she also knows that Mirror Burnham was a co-conspirator working with Lorca during his attempted coup.
Georgiou decides to have Burnham executed for treason. With no choice left, Burnham reveals that she's from a parallel universe. This interests Georgiou. The Emperor and Burnham work out an agreement where Georgiou will let Burnham go in exchange for schematics of Discovery's spore drive.
Georgiou, Burnham, and Saru work out a rendezvous point. That's when Georgiou lets Burnham know about her relationship with Lorca. Lorca was Burnham's father figure when she was young. When she got older, they became romantically involved.
That information makes everything click for Burnham. First, she notices that Georgiou is sensitive to light the same way Lorca is. Lorca claimed it was a result of the destruction his previous ship. Georgiou lets Burnham know that its a genetic difference between mirror universe humans and prime timeline humans. Burnham remembers how fixated Lorca was on her, going out of his way to get her out of prison. She remembers how Lorca dodged questions about how Discovery ended up in the mirror universe.
That's when she pieces together that her Lorca is Mirror Lorca. Lorca somehow – by design or accident – ended up in the prime timeline. He manipulated Stamets into bringing them back and he made sure to bring Burnham with him because it was the only way to get on board the Emperor's palace ship alive.
It seems like Lorca is ready to attempt another coup, and this time Discovery's crew may be caught in the crossfire.
New Star Trek: Discovery episodes become available to stream Sundays at 8 p.m. ET on CBS All Access.