After Cronus lies dead and the Labs are relatively safe, Tanaka informs Alpha Co that he needs to be protected while he finishes his research. Alpha grudgingly agrees, as they have no other leads. They must then protect the doctor as he moves about the Laboratory to work on his research.
All the while the labs will be assault from enemies on three fronts. Enemies will emerge from Bio-Domes C and D, climb into the labs through an entrance to the south, and unburrow inside the labs themselves.
The team must split their attention. Classes with powerful AoE skills such as Forward Observers and Commandos as well as any Flamethrowers should hold the entrance. These classes bombard the area outside the entrance with withering firepower to kill the bulk of the horde before they even get close.
The hordes that appear outside are primarily Infested Marines, with Hulks, Zombies, and Agrons mixed in. Generally the Stinger MK-3 and any XM814 Heavy Machine Guns should be put to good use holding the outside. Be very wary as Huggers will also appear occasionally and should be dealt with immediately.
Inside the labs, the primary enemies are a mixed of Hulks, Zombies, and Stalkers. Occasional Gargoyles may fly in from outside. Seekers will also appear in number depending on the difficulty. Players protecting Tanaka inside should stick to Flamethrower MK-3s, 590A5 Combat Shotguns, and M5 Pulse Rifles.
When the hordes finally start to wear down, Tanaka reveals all his progress was a trap. He then floods the area with Noxious Gas, disorienting the Marines, and attempts to escape.