Comms Officer Samantha has uncovered a distress signal coming from Grissom Academy a school for young biotics and engineers. Edi and Samantha note that his is quite similar to the false signal used by Cerberus to trick Shepard into previously entering the Collector base awhile back. Once on the planet it is discovered that Cerberus is indeed there and kidnapping the young students, to probably for experiments on them.
Shepard runs into Jack who has become an instructor for the young biotics and she of course wants to fight to keep them out of the hands of Cerberus operatives who would damage them as they did her. Shepard ends up commandeering and abandon enemy mech to safeguard the students escape along with Jack.