As the Federation recovers from the devastating events of Star Trek: Destiny, Captain William Riker and the crew of the U.S.S. Titan are ordered to resume their deep-space assignment, reaffirming Starfleet's core principles of peaceful exploration. But even far from home on a mission of hope, the scars of the recent cataclysm remain with them as they slowly rebuild their lives.

The planet Droplet is a world made mostly of water without a speck of solid ground. Life should not exist here, yet it thrives. Aili Lavena, Titan's aquatic navigator, spearheads the exploration of this mysterious world, facing the dangers of the vast, wild ocean. When one native species proves to be sentient, Lavena finds herself immersed in a delicate contact situation, and Riker is called away from Deanna Troi at a critical moment in their marriage.

But when good intentions bring calamity, Lavena and Riker are cut off from the crew and feared lost. Troi must face a life-changing event without her husband, while the crew must brave the crushing pressures of the deep to undo the global chaos they have triggered. Stranded with her injured captain, Lavena must win the trust of the beings who control their fate — but the price for Riker's survival may be the loss of everything he holds dear.