Satsuriku no Tenshi / Angels of Death 1x12

Floor B1 looks like an ordinary residence. After following a trail of blood to what appears to be a living room, Rachel suddenly panics. She pressures Zack to kill her immediately, then passes out. Then Danny appears, only to shut Zack out of the room and tell him, "If you succeed in learning everything, I'll open the door." So Zack sets off to search the floor on his own for the truth...