The capture of the USS Enterprise in 2259 by the pirate crew of the Serene Squall, whose captain, Angel, hoped to exchange Spock for a Vulcan prisoner.
A former Starfleet counsellor calling herself Doctor Aspen persuaded Captain Pike to take the Enterprise beyond Federation space to rescue stranded colonists. It was a trap. Pike and most of the crew were captured aboard the pirate ship Serene Squall, and Aspen revealed herself as its captain, Angel.
Angel demanded that T'Pring, who worked at a Vulcan rehabilitation centre, release a prisoner named Xaverius in return for Spock. Spock and Christine Chapel staged a romance so that T'Pring would have cause to break their bond and refuse. Pike meanwhile stirred up a mutiny on the pirate ship and retook his own.
The episode, The Serene Squall, ends with Spock realising that the prisoner is his half-brother Sybok.