In Amber Clad made a blind jump following a Covenant cruiser on unknown trajectory. They came out of hyperspace in orbit of another Forerunner Halo. Captain Keyes gave the orders to disrupt Covenant operations, and if possible capture their Prophet of Regret. The Master Chief got the capture mission. Your team drew the "cakewalk" assignment of retrieving some Index from a library. Sounds easy, but it never is. Based on the video game series.