Blue Dogs from Venus
The story begins with Captain Kirk's voiceover announcing the completion of the shakedown cruise of the refitted Starship Enterprise. We see several short scenes from various parts of the ship, showing the crew busy with their tasks, the last of which is a scene with Kirk, Spock and McCoy in the recreation lounge toasting to the successful start to another 5 year mission. Their celebration is interrupted by Lieutenant Uhura, who informs Kirk that there is an urgent transmission from Starfleet for his immediate attention. Kirk learns that there is a hostage situation near the Romulan Neutral Zone involving Starfleet's covert branch and that the Enterprise must intervene to resolve the situation without endangering the fragile Romulan peace treaty.
As the Enterprise departs the Jupiter Shipyards, Track 1: Star Trek Theme accompanies the opening credits.
We next see the Enterprise entering orbit around Danos III, a small planetoid near the Romulan Neutral Zone that is home to a seldom used diplomatic station. Lieutenant Sulu reports another ship in orbit: the Starfleet Operations scout class vessel named Cygnus. Uhura pipes a hail from this ship to the Captain's Ready Room so that Kirk can learn more about the hostage situation from the Diverse Operations Group Captain Talia Black. As Track 2: Blue Dog Anthem/Talia's Theme plays, Black reports that her son has been taken hostage by a small group of Romulan soldiers demanding that Danos III be designated as Romulan territory owing to recent findings of ancient Romulan artifacts on the planetoid. Kirk, who has heard of the impressive service record of this "Blue Dog from Venus" offers to negotiate the situation and, if necessary, bring the might of the Enterprise to bear. He invites Talia and her landing team on board the Enterprise to coordinate their plan. She accepts but claims that there is a technical issue on board her ship that she must address first.
As Kirk returns to the bridge to inform the crew of their mission, a bright blue light envelopes the bridge. Track 3: Enterprise in Peril begins as we see a foggy beam of blue light emit from the Cygnus and surround the larger starship. Instead of signalling red alert, Kirk takes his command seat and happily orders the crew to prepare a full honours celebration meal to welcome the Blue Dogs onboard. All the bridge officers onboard heartily agree to this plan, except for Spock, who claims sudden fatigue and excuses himself to sickbay.
Talia and her crew are beamed aboard the Enterprise by Lieutenant Commander Scott. He seems to be very delighted to see them and accompanies the team to the Enterprise's bowling alley, which is being converted into a banquet hall by the crew. There are a few scenes showing the preparations, including the cooks in the ship's mess and the set up of a band featuring Uhuru as lead singer. As the guests await the main meal, Uhuru entertains them with Track 4: Hail My Frequency Now, a slightly risqué torch song in which Uhuru expresses her feelings for the Captain, First Officer and the ship's Doctor.
Meanwhile, in sickbay, McCoy is trying to concentrate on diagnosing Spock's condition while fending off amorous advances from the nurses. Spock is in pain but manages to make McCoy question why the entire crew is so jovial and is bursting out into spontaneous song. No one other than Spock seems to have any recollection of the mysterious blue field that surrounded the ship. Kirk visits sickbay to get an update on Spock's condition and after a mind meld the Captain realizes that the Blue Dogs must be attempting to control the crew. With his mind conditioned by the meld, Kirk races to the bowling alley after unsuccessfully recruiting security personnel to accompany him. He manages to persuade Talia to have a friendly chat about the rest of the festivities, separating her from her team to confront her about the apparent attack. Talia, realizing Kirk is breaking the influence of her mind control forcefield, activates a personal field emitter that strengthens the effect. Kirk bursts out into Track 5: Not on My Ship as he desperately attempts to persuade Talia to remove the forcefield. As he sings this song, Talia confesses to him that the motive for the hostage situation was not a matter of territory but rather an attempt to force her to capture the Enterprise for High Commander Satek of the Romulan Guard as part of his attempt to stage a coup. Talia and Satek had recently ended an affair, a relationship she started so that she could gain intelligence on Romulan activities in the sector. Kirk demands that he take control of the situation without the forcefield's influence but Talia renders him unconscious with one final exposure to her personal field emitter.
Talia returns to the feast, having hidden the unconscious Kirk in an observation lounge. The party is in full swing as Scotty entertains the crew and guests with a bawdy rendition of Track 6: An Aberdeen Pub Crawler, in which he compares the adventures of his crew to a night of bar hopping in one of his favourite towns. The entire group is caught up in the song, except for Talia and two of her team, who quietly slip away to the bridge, which they commandeer from the skeleton crew and proceed to set course deep into the Romulan Neutral Zone.
Spock is awakened in sickbay by the shipwide transmission of the music and festivities in the bowling alley. McCoy injects Spock with a neural relaxant which alleviates his pain and allows Spock to think clearly, though he apparently can only sing, not speak, his concerns to McCoy. Realizing that the ship may be in peril, Spock leaves sickbay to find the Captain but not before instructing McCoy to concoct a similar relaxant for human physiology. As Spock attempts to locate Kirk, he sings Track 7: It's Logical, a bittersweet song in which Spock confesses his mix of admiration and frustration in serving with such an emotionally-driven Captain, drawing parallels to his own struggle with his half-human, half-Vulcan heritage. The song ends on an upbeat note as Spock discovers Kirk who is slowly regaining consciousness. Spock applies a deeper mind meld to Kirk and temporarily eliminates the forcefield influence from the Captain. Kirk, however, is still amused at Spock's need to sing every word.
Back in sickbay, McCoy and the nursing staff concoct a mixture to neutralize the effects of the forcefield while singing the rousing Track 8: Just a Country Doctor. McCoy makes sure that the mixture has the correct green colour so that it can remind him of his favourite mint juleps just like they make back home. Confident that he has the correct formula, he instructs his staff to flood the atmospheric control system with the green mist.
As the crew realize what is happening, Kirk and Spock burst onto the bridge and take control of the ship, just as three Romulan Warbirds decloak ahead of them. Kirk has Talia brought to the bridge and forces her to give the override codes for the Warbirds, which she recognizes as Satek's ships. A montage of several scenes follow as engineering, weapons control, security and the bridge all belt out Track 9: The Finest Crew, a sea shanty style song that motivate the crew to disable and then outrun the Romulan threat as a security team detains Talia and her Blue Dogs in the brig.
Upon returning to Federation space, the crew finally shakes the effects of the blue field and the Enterprise sets course for Starfleet Command to turnover the Blue Dogs for trial. The last scene has Kirk addressing Talia outside the brig forcefield, with him promising to do what he can to rescue her son from the Romulans. She thanks him for his promise and blows him a kiss, then disappears after tugging on her left earring. Kirk hails the bridge and orders internal and external scans, but Talia is no where to be found. Spock surmises that Talia has acquired advanced alien technology and that she is likely going to attempt a rescue of her son on her own. As the Enterprise enters the orbit of earth, Track 10: End Titles, plays.