Kim Se-hoon, the guy on the 15th floor, goes missing. Sae-bom and Yi-hyun try to figure out why he disappeared and what he was trying to hide. The residents in the building flock to his unit and squabble over the supplies he had stashed. Meanwhile, Yi-hyun contends with his thirst and keeps Sae-bom from knowing about his infection. (thetvdb.com)