With no understanding of what the tower is or why they've been chosen, thirteen seemingly random strangers must battle to reach the top of a tower before the countdown clock reaches zero... and the world faces a potentially catastrophic fate.

When a mysterious tower appears in the skies over England, thirteen strangers are pulled from their lives to stand before it as a countdown begins. Above the doorway is one word: ASCEND.

As a grieving teacher, a reclusive artist, and a narcissistic celebrity children's author lead the others in trying to understand why they've been chosen and what the tower is, it soon becomes clear the only way out of this for everyone... is up.

And so begins a race to the top, through sinking ships, haunted houses and other waking nightmares, as the group fights to hold onto its humanity, while the twisted horror of why they're here grows ever more apparent - and death stalks their every move.