Uhura documents the Enterprise’s encounter with a naturally occurring subspace fold. In order to test Spock’s theory the fold can increase the speed of communication, Uhura is busy patching communications through manually because the experiment requires so much computer power.

Pike is expecting Batel. Una is expecting James Kirk. Chapel is waiting on a communication from Dr. Korby. Spock is waiting for Uhura to continue the experiment.

Batel proposes a trip together to a planet Pike deems touristy. Pike makes excuses to put off planning the trip.

Kirk beams aboard just as Una notices La’an seems nervous. He’ll be spending some time on the Enterprise, shadowing Una in preparation for his promotion to First Officer on the Farragut. His arrival flusters La’an.

In sickbay, Chapel doesn’t want to open Korby’s communication in case it’s another rejection. She really wants a fellowship with him, calls him a genius. Only five people out of the thousands of applicants will be accepted.

Chapel finally reads the communication and she’s been chosen. She’ll be gone for three months.

In Engineering, Pelia asks why Spock and Uhura think the subspace fold will improve communications. Uhura explains the improvements they think could happen but so far nothing’s worked. Uhura hums as she prepares for their next try. Pelia suggests they send music through.

Spock asks Uhura to choose a song. She chooses “Anything Goes” and it elicits a reaction from the fold, sending a wave through the ship.

Pike orders a shipwide check in. Spock starts reporting from Engineering except he sings his report. Sickbay follows suit. On the bridge, Ortegas and Una both sing their reports. Ortegas and Mitchell discover their movements are now synchronized.

La’an and James Kirk join the bridge and the chorus.

Opening credits soundtracked with a choral rendition of the theme song.

In Pike’s ready room, they debrief the experience. Spock hypothesizes the song they sent into the fold created a quantum uncertainty field that has forced the ship into a reality where people sing uncontrollably. He shows that the ship has become tethered to the musical improbability field, so there will probably be more singing.

Seeing as the Enterprise seems to be unzipping the field and making it bigger, the team suggests they can reverse it and zip the field back up into the fold.

As Spock and Uhura try to find the frequency of the song that opened the fold, Spock notices the communication from Korby on Uhura’s screen. He asks if it’s about the fellowship application. Uhura assures him she does not look at the crew’s personal communications.

He admits that he and Chapel are more than colleagues but that they aren’t really talking at the moment.

James Kirk and Una discuss strategies for commanding a crew as First Officer. Una suggests being connected to the crew is a positive. In song.

La’an overhears and sees their duet and dance. She looks concerned.

She returns and begins a solo number, wondering if the effect of the musical improbability field will cause her to spill her secrets and feelings too.

Belting out some emotional truths in her quarters, she imagines her and the alternate timeline James Kirk together.

She reports to Pike the potential security threat of the musical improbability field as it cause people to reveal their emotional information uncontrollably.

Uhura contacts Kirk to begin the attempt to close the zipper. James and Sam are working together at the time and both respond to Uhura’s message.

The deflector shield shot appears to work momentarily but then the fold bursts open again. Just then Batel contacts the Enterprise from the Cayuga. She’s put on-screen and she and Pike have a duet, airing their relationship issues for the crew to see and hear.

La’an runs across and cuts the com just as Pike falls to his knees to declare his love for Batel.

Pike asks why Batel, who is on another ship, is singing too. Spock and Uhura inform him that the field has spread through the subspace network to the entire fleet.

Pike suggests they blow up the fold. Spock says the idea has merit but they should test it on a small sample of the fold’s subatomic particles. La’an and James Kirk are tapped but La’an wants to refuse the assignment.

Una talks with her about how keeping secrets becomes a habit that’s hard to break.

Working with James Kirk, La’an decides to tell him about the time travel adventure but is interrupted when the subatomic particles they isolated and sent to Engineering blow up.

Blowing up the field is not an option.

The Enterprise is hailed by a Klingon ship. Although Pike keeps Uhura from opening a channel, she informs him the ship has already been affected by the field. The transmission informs them that the Klingons plan on firing on the fold.

In a planning meeting, they note they have two hours before the Klingon ship arrives. Una assigns La’an the mission of creating a tactical strategy. La’an taps James Kirk to work with her on it.

Pike tells Spock and Uhura to figure out a way to shut down the field. They figure if they can track the field’s frequency when a song breaks out, they might find out how to break the field. All they need is some extreme emotion to trigger a musical number.

Uhura directs Spock's attention to the bar where Chapel is celebrating getting the fellowship. He asks why she hasn’t told him yet. This triggers Chapel’s number where she declares herself ready for new adventures, even if it means leaving Spock. It’s a big ensemble piece.

La’an and James Kirk discuss the targets on a Klingon ship. Kirk asks La’an about what she wanted to talk to him about. La’an spills about the other James Kirk and how she felt about him. This James Kirk reveals that he’s in a complicated relationship and Carol is now pregnant.

Uhura checks in on Spock in Engineering. He’s analyzed the data and can’t find a pattern. He’s upset by Chapel’s willingness to leave him. He gets a solo that parses out his choices around Chapel.

Spock rushes out of Engineering, leaving Uhura to solve the problem. She gets a solo about her family and how she’s always alone. Her vocation is to keep everyone connected. She finds the pattern.

She reports to Pike that there’s a spike in the field every time someone sings. She tells him if they can get the spike high enough, it’ll shatter the field. It requires a grand finale ensemble number, everyone singing and dancing together.

Pike tells Uhura she’s the one to inspire the crew to unite in this number.

Pike addresses the ship and orders them to follow the Voice of the Enterprise, Uhura.

She takes over and tells them that she always felt alone until she joined the Enterprise. She reminds them of the connection they have to each other as members of the crew.

It sparks the spirit of the crew collectively and the musical number spreads.

Uhura’s monitoring the spike and calls for more voices. Pike orders a channel opened to the Klingons who are in the middle of their own number.

On the final note, the field shatters. Chapel and Spock share a sad glance and part ways.

Una checks in with La’an. She admits it hurt to be honest with James Kirk, but she’s glad she took the chance and resolves to take chances more often.

Pike cooks for Batel. She tells him that he needs to be honest if their relationship is going to work.

Uhura reports all Federation ships are back to normal. Pike asks her to open a channel to non-Federation ships in the area so they can share their findings. She’s humming as she works and everyone stops to look her way. She confesses it’s just an earworm and carries on.