Choose Your Pain

After a month of successful operations, Lorca is ordered to protect the spore drive until it can be replicated for other Starfleet ships. As he returns to the Discovery, Lorca is taken captive by a group of Klingons led by L'Rell. Burnham has grown concerned by the toll that the drive has taken on Ripper. Along with Stamets' partner, medical officer Hugh Culber, Burnham convinces Stamets to find an alternative to run the drive. Lorca is imprisoned with captured Starfleet officer Ash Tyler and human criminal Harry Mudd, and in discussions Lorca reveals that he killed his entire crew during an earlier battle to spare them from the Klingons' torture, but escaped himself. Lorca is tortured by L'Rell, who wants to learn the secret behind Discoverys new form of travel, but Lorca and Tyler escape before the Klingons can learn anything about it.

Summary from Wikipedia, CC BY-SA 4.0.