Burnham defeats Osyraa, Book uses the spore drive to reach the nebula, Saru helps Su'Kal escape, and Burnham becomes Discovery's captain.
Unable to jump without Stamets, Osyraa cuts off life support to the captive bridge crew. Tilly and the others sabotage a nacelle to drop Discovery out of warp, and Burnham reaches the ship's computer core, kills Osyraa and restores the crew's systems. Aurellio suggests that Book's empathic abilities could let him navigate the spore drive, and he jumps Discovery to the nebula.
There Saru helps Su'Kal leave the simulation and come to terms with his mother's death. Burnham is promoted to captain, the Emerald Chain collapses, and Discovery begins delivering dilithium to worlds cut off by the Burn. Michelle Paradise wrote the season finale.