"The Babysitter" follows a squad of four Orbital Drop Shock Troopers, or Helljumpers. The squad is composed of Private O'Brien, Dutch, Master Sergeant Cortez, and Corporal Checkman. O'Brien is being replaced as the squad's sniper by Cal-141, a SPARTAN-II, and is now the backup. The squad is sent into a Covenant zone under the cover of a meteor shower to eliminate a Prophet.