Jia Jem Wearing Costume From Mass Effect 2

The Illusive Man reveals that a human colony known as Horizon, is under Collector attack, and dispatches the team to save the colony. He notes that one of Shepard's surviving crew members, either Kaidan Alenko or Ashley Williams depending on who the player sacrificed on Virmire in the first game, is stationed at the colony. Shepard arrives and battles the Collectors in an attempt to save the colony. The Commander stops the Collector attack by re-activating the colony's defense batteries forcing the Collectors to flee on their ship. Shepard saves only half of the colonists, the Collectors abduct the rest. Shepard then reunites with a former team member, who leaves feeling betrayed by Shepard working for Cerberus.
It is later revealed on the Normandy that the Illusive Man leaked a tip about Shepard being alive to the Alliance and that the Collectors intercepted this message indicating that the Collectors have a personal interest in Shepard. Shepard is also provided with additional dossiers on more potential recruits: an asari Justicar, a drell assassin, and Tali. The Justicar, Samara, joins the team after Shepard investigates the Eclipse mercenary group and its involvement in a murder. The drell assassin, Thane Krios is in the midst of an assassination mission. Learning of Thane's next target, Shepard finds Thane, who dispatches his target and joins the team. Tali is found in the outer rim of the galaxy, running a scientific survey that comes under geth attack. After she is rescued from an immense geth force, Tali joins Shepard.
The Illusive Man contacts Shepard again after intercepting a turian emergency transmission, claiming a turian battle group engaged and disabled a Collector ship before being destroyed. Believing valuable information could be learned from the Collector ship, Shepard and his team locate the ship. Inside the ship, Shepard learns that the Collectors were originally captured Protheans that were indoctrinated and genetically altered to become slaves of the Reapers. The Collectors that Shepard has encountered are under the direct control of a Reaper named Harbinger. With EDI's help, Shepard locates information on how to bypass the Omega-4 relay, but the derelict ship turns out to be a Collector trap, and Shepard and his team are forced to battle back to the shuttle and escape before the Collectors can destroy the Normandy. EDI also determines that the Illusive Man knew the signal was a trap but dispatched Shepard to the collector ship in order to gain more information about them. When questioned about this, the Illusive Man argues the deception was necessary in order for the Collectors to believe they had the upper hand and that alerting Shepard to this could have tipped off the Collectors.