It's a sink-or-swim mission when Luke and the team dive into deadly waters to stop a sinister terrorist from making a massive splash.

A face from the past threatens Luke and Tally's recharged romance. The team breaches a fortified compound to keep vital intel out of enemy hands.

As Greta attempts to loosen Luke's lips, the safe-house gang gets an earful from afar. Emma turns heads on the dance floor with an unlikely date.

While Cress tightens the screws, Chips matches wits with an interrogation expert. A stealth mission makes a bigger bang than expected.

Barry hitches a ride to the final frontier. As an operative's cover story begins to crumble, Luke and Emma seek help from an unexpected ally.

Emma and Luke catch a buzz in a deep-sea submersible. Back on land, bullets and breadsticks fly in a confrontation at a pizza joint.

Every second counts as the team scrambles by land, air and sea to avert a catastrophe. Aldon finds himself outnumbered - but not outmatched.

As the clock ticks down to zero hour, Luke and the crew must break into a top-secret facility before their adversary turns off the lights - for good.