Lazlo is located in the quarantined area and you probably saw him whenever you were doing Quarantine: Infestation. It turns out he was the one who released the infection and he now wants you to rescue his friends, by freezing them. Begin by grabbing the Freezeasy weapon from the trash pile and equip it.

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Grab the Freezeasy and use it to freeze the enemies in the next room, picking up the chunks that drop.

Jump across the gap and to the catwalk where Lazlo went, then wait for him to open the door. A bunch of infected enemies will spawn, so just freeze them with the mission weapon. It seems that the enemies will shatter after a second or two of being frozen, breaking up into chunks. You’ll need to pick up a total of 12 of these chunks. Place them in Lazlo’s room, then talk to him to finish the mission.