The mission starts when Kuo calls Cole and informs him that their Ice Soldier Ally wants to meet again. She also tells Cole that their ally has "changed" since they last met. Cole must find his ally, who informs him that several Corrupted creatures are terrorizing the area.
Cole must then follow the Ice Soldier ally across Flood Town to the rail yards. It is there they find the monsters terrorizing the citizens, with the New Marais Police trying to fight the monsters off and protect the civilians. After all of the corrupted have been defeated, Cole's ally thanks him as the civilians surround them to cheer. His ally tells him that the people owe them their lives before saying they must not be seen together, then departs.
For this mission, you'll need to defeat a couple of corrupted creatures. Cole's Ice Grenades can prove very effective against these creatures. If a bunch of spikers appear, using Cole's ionic powers may pay off. Just make sure no civilians are around.