It's been 21 days since the hundred landed on Earth. They're the only humans to set foot on the planet in centuries ... or so they thought. Facing an unknown enemy, WELLS attempts to keep the group safe after a tragic attack. CLARKE strikes out in search of other colonists, while BELLAMY is determined to rescue his sister, no matter the cost. And back on the ship, GLASS faces an unthinkable choice between the love of her life and life itself. Secrets are revealed, beliefs are challenged, and relationships are tested. The hundred will struggle to survive the only way they can - together.