User blog comment:The Illusive Man/Arrival: If the timer hits zero.../@comment-1221773-20110329190107/@comment-743796-20110330012304

This doomsday scenario resembles that of the Legend of Zelda: Majora's Mask. If you allow the clock to wind down without playing the Song of Time to travel back to Day 1 from Day 3, then at 5 AM just before Day 4, there is a destructive cutscene showing the Moon obliterate Clock Town, with the Clock Tower getting destroyed first.