The novel follows up on the events of "Unification I" and "Unification II". When Romulan authorities arrest a group of Unificationists including Ambassador Spock on the planet Constanthus, the Federation must mount a rescue before Spock's identity is revealed to the Romulans. Captain Jean-Luc Picard and the crew of the USS Enterprise-D accompanied by Admiral Leonard McCoy must travel into Romulan Space to rescue them. At the same time Captain Montgomery Scott sets out on his own mission.
- Became Their Own Antithesis: After McCoy becomes frustrated with Picard's apparent hesitation and unwillingness to take decisive action during the negotiations with the Romulan Senate to take custody of the Unificationists, McCoy officially takes command of the Enterprise and tries to negotiate directly with the colony governor that captured the Unificationists. However, this results in the colony governor realising that he has Spock in custody, ending negotiations as the possibility of interrogating Spock offers far more benefits than any deal he could make with the Federation. Faced with this revelation, McCoy retreats to Ten-Forward, bitterly musing that he has become the kind of admiral he always hated when he was on the Enterprise, the admiral who steps in and takes over thinking he knows everything only to reveal that he actually has no idea and ends up making the situation worse.
- Becoming the Mask: The spy winds up coming to believe in Surak's philosophy and refuses to identify Spock.
- Big Damn Heroes: Scotty transports Spock and the Unificationists out of harms way just in time.
- Big Damn Reunion: Scotty's Big Damn Heroes moment above leads to him and Spock meeting for the first time since he awoke in the future.
- Break Out the Museum Piece: Scotty steals the USS Yorktown and an old-school Romulan cloaking device from a Starfleet museum to rescue Spock. He's aware that neither will hold out for long if he has to fight, but they're good enough that he's able to basically take the Romulans by surprise.
- But for Me, It Was Tuesday: Invoked; while Spock is surprised to see Scotty basically unaged after an absence of over seventy-five years, he reflects that if anyone could find a way to pull that off he's not surprised that it was Montgomery Scott.
- Call-Back: Numerous ones to TNG and TOS
- Star Trek S3 E2 "The Enterprise Incident": The cloaking device acquired in that episode plays a central part in Scotty's plan to enter Romulan space.
- Star Trek S2 E24 "The Ultimate Computer": Scotty refers back to this episode when putting together a control system for the Yorktown that allows him to run it by himself.
- Star Trek S1 E4 "The Naked Time": Kevin Reily's son shows up and Scotty refers back to the episode's events to convince him to help.
- Star Trek S2 E13 "Obsession": The USS Yorktown return from that episode having been converted into a museum which Scotty steals in order to get to Constanthus.
- Star Trek: The Next Generation S1E1 "Encounter at Farpoint": Admiral McCoy's visit to the Enterprise-D and Data's tour are referenced.
- Star Trek: The Next Generation S6E4 "Relics": Scotty returns still piloting the shuttlecraft from that episode and one again encounters the original Enterprise bridge.
- The Enterprise's original bridge module was removed during the refits prior to Star Trek: The Motion Picture.
- Chekhov's Gun: The strange behavior of the Stugg is introduced early on and the odd movements of Romulan vessels are noted several times by various characters, before McCoy realizes that both side are building up for a potential conflict and uses that information to make the Romulans back down.
- Face Death with Dignity: Spock and his student refuse to bend even in the face of death.
- Establishing Character Moment: McCoy's frustration with how hesitant and timid Starfleet has gotten in his view is nicely set up in his first chapter.
- Hero Insurance: McCoy pulls some strings at the end to get Scotty off for stealing the USS Yorktown to save Spock.
- I Am Spock: The Unificationists pull this off to prevent Spock from giving himself up to save them.
- Jerkass Has a Point: At the end, Picard concedes McCoy was right that decisive action was necessary to save Spock.
- Jerkass Realization: As McCoy notes he always hated it when some self-important Federation official was on board his Enterprise back in the day, now he's realized he was acting exactly the same way.
- Jerk with a Heart of Gold: Admiral Leonard McCoy clashes with Picard over his handling of the mission and winds up reliving him of command at one point, but he's desperate to save one of his few remaining friends.
- My God, What Have I Done?: McCoy, when he realizes his presence gave away that Spock was among the Unificationists
- Nice Job Breaking It, Hero: McCoy and Scotty wind up giving Spock away when the Romulans look up their service records.
- Obfuscating Insanity: Scotty acts like he's a delusional war hawk out to get the Romulans, to throw them off when they capture him.
- Pragmatic Villainy: The Romulan Procounsel is forced to let the Enterprise-D go when McCoy points out that the Romulan Empire can't afford to start a war with the Federation due to the potential conflict with the Stugg.
- Rescue Reversal: Riker, Data, and La Forge wind up having to be rescued by Scotty after they get captured by the Romulans looking for him after he'd already escaped.
- Screw Politeness, I'm a Senior!: McCoy doesn't hesitate to loudly call out Picard on his own bridge.
- Still Wearing the Old Colors: Scotty dons the old Red Shirt uniform again on the Yorktown, noting it feels a little embarrassing but he needed something fresh to wear.
- Title Drop: Picard notes that Constanthus means "Crossover" in Romulan.
