For years, Starfleet Intelligence agents have carried out undercover assignments deep within the Klingon Empire. Surgically altered and rigorously trained in Klingon culture, they operate in plain sight and without any direct support, while collecting information and infiltrating the highest levels of imperial power. Their actions have given Starfleet valuable insight into the inner workings of Klingon government and its relentless military apparatus.

After three of Starfleet's longest serving agents fear exposure, they initiate emergency extraction procedures. Their planned rendezvous with the USS Endeavour goes awry, threatening to reveal their activities and the damaging intelligence they've collected during their mission. Tasked by Starfleet to salvage the botched rescue attempt, Captain James T. Kirk and the crew of the USS Enterprise must discover the truth behind a secret weapons experiment while avoiding an interstellar incident with the potential to ignite a new war between the Federation and one of its oldest adversaries.