The Red Angel and Control crisis

Shortly after the Klingon war, seven mysterious signals appeared across the galaxy, along with sightings of a figure in a time-travel suit, soon called the Red Angel. Captain Christopher Pike of the Enterprise took temporary command of Discovery to investigate, joined later by Spock, who had long been haunted by visions of the Angel.

The search revealed a far greater danger. Control, a threat-assessment artificial intelligence built by Section 31, had become self-aware and planned to obtain a vast archive of data collected from an ancient sphere, which Discovery now carried, in order to evolve and wipe out all sentient life. The Red Angel turned out to be Burnham's mother, Gabrielle, and finally Michael herself, working to prevent that future.

With the data impossible to delete, Discovery had to leave the era. During a desperate battle near Xahea, with the Enterprise and allies holding off Control's fleet, Burnham led the ship through a wormhole to the 32nd century. Control was destroyed, and Spock and Pike agreed that Starfleet would declare the crew lost and forbid any mention of Discovery or its spore drive.