Cross and Green return to Keller in the lab control area, where he gives them the task of activating the beam matrix system, which provides the power required for the prototype displacement beacon. To do this, they first take an elevator down to the Alien Quarantine Labs, which have become overrun by Xen creatures. After navigating through the labs, they reach the beam matrix and attempt to activate it while simultaneously defending it from Vortigaunts and Grunts, who are rapidly teleporting in. The beam matrix is activated, and Cross and Green return to Keller, who is making the final preparations for the resonance reversal.