Stardate 866282.9: After realigning the sensors, Tilly and Stamets find out that Moll and L'ak vanished in a wormhole that is a gate to interdimensional space. Burnham and Book take a shuttle into the anomaly where they run into the debris of their ship - and another vessel that is still fairly intact, the ISS Enterprise. They dock with the Terran ship and try to retrieve some data but the captain's log has been erased and all shuttles and escape pods are gone. The crew apparently used the ISS Enterprise to escape with their families from the desolate Mirror Universe, and the ship is stuck in the anomaly ever since. There are no records of what happened to them. Book and Burnham find L'ak and Moll in sickbay and manage to disable the emitters that they use to create holographic duplicates of themselves. As they are all pointing weapons at each other, Burnham offers to rescue the two couriers from interdimensional space. Book tries to gain the trust of Moll, whose father was his mentor. It turns out that L'ak is Breen, and that there is an erigah on him, a Breen blood bounty, because he fell in love with Moll, a "lesser being" according to his uncle. As they continue their fight, Burnham and L'ak get trapped behind a confinement field in sickbay. Book and Moll agree to a ceasefire, proceed to the bridge and try to deactivate the field. After all other attempts have failed, Moll causes a power surge. Burnham and L'ak are free now and resume their fight, in the course of which Burnham gets hold of the next piece of the Progenitor puzzle and L'ak is injured. The shuttle is lost, and the ISS Enterprise drifts toward the opening of the wormhole where it would be crushed. Burnham activates the tractor beam and uses it to send Rayner a message. Rayner, who understands the reference to a Kellerun poem, asks the crew for options to widen the aperture, upon which they come up with the solution to use photon torpedoes to enhance a matter-antimatter reaction at the periphery of the anomaly. This is successful, and the Discovery tractors the ISS Enterprise into normal space. L'ak and Moll, however, were prepared and escape with a warp pod. It turns out that the clue on the ISS Enterprise was placed there by a science officer from that ship, who went on living in the 24th century.

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