In 2256 Harry Mudd used a time crystal to trap the USS Discovery in a repeating half hour while he worked out how to steal the ship.
Mudd planned to sell Discovery and its spore drive to the Klingons, and each time a plan failed he reset the loop and tried again, killing Captain Lorca many times along the way. Because of his exposure to the mycelial network, Paul Stamets was the only crew member who remembered each cycle.
Stamets enlisted Michael Burnham and Ash Tyler, and over repeated loops they turned Mudd's method against him. Finally they tricked him into ending the loop, and he was handed over to his wife, Stella, and her father.