With his back in severe pain, Odo hobbles into the infirmary convinced that he has become infected with Alvanian spine mites. However, Doctor Bashir diagnoses a pinched nerve resulting from bad posture and advises that Odo try some of Worf's morning exercise classes. Quark, intruding, suggests he try a holosuite program featuring three Orion slave girls instead, much to Odo's annoyance. Unperturbed by the Constable's hostility, Quark explains that he has obtained something from a Yridian dealer that Odo might be interested in – a dead Changeling, contained in an ornate container. After settling a price of 8 slips of gold-pressed latinum upon realizing that the Changeling is actually alive, but sick, Quark sells it to Odo. Bashir advises placing the Changeling into a containment field but Odo assures him there's no need – it is just an infant.
In the Infirmary, Captain Sisko and Odo regard the sick and discolored infant Changeling. Odo explains that when he was found, he was as small as the infant in front of them; its mass will increase as its shapeshifting abilities develop. Bashir concludes that the infant was exposed to a massive amount of tetryon radiation, and that he will have to purge the isotopes with an electrophoretic diffuser.
Sisko asks Odo if he's sure the infant poses no threat. Odo explains that when he was found he had no idea of what he was or where he was from – what better way for the Hundred, and therefore the Founders, to gauge other species than by the way they treated the weak and vulnerable. When Sisko suggests that valuable intelligence could be gained by studying the infant, Odo asks that he be allowed to work with it, to teach it to shapeshift. Sisko proposes that Odo contact his old mentor, Doctor Mora Pol, for help, but Odo states that he would rather do it alone.
Some time later, Bashir reports that the purge was almost 100% successful. He says he must leave to check on Major Kira, who has gone into labor with the O'Briens' baby, but Odo is preoccupied by thoughts of the infant. Before he leaves, Bashir advises that there is still a small degree of instability in the infant's morphogenic matrix and that he has set the computer to monitor for fluctuations. Once Bashir has gone, Odo begins to talk softly to the infant, explaining how he spent months in a lab being studied and how he felt lost and alone. He promises that it won't be that way this time.
In a birthing room, a Bajoran midwife, Miles and Keiko O'Brien use percussion instruments to sound out a soothing rhythm as Doctor Bashir examines Major Kira. Miles struggles to keep the rhythm and complains that the birth is taking longer than expected. Bashir explains that for Bajoran women, giving birth is all about being relaxed; Miles counters that Kira will not relax until First Minister Shakaar arrives – just then he does, hours late.
Seated at a table in the Replimat, Odo talks to the infant Changeling, which is now contained within a drinking glass. He is interrupted by Worf, who asks why Odo is talking to his beverage. Odo explains that it is a Changeling, causing Worf to look uncertainly at his own drink.
Back in the science lab, Odo explains with wonder to the infant that it is a Changeling, a shapeshifter, and that it could be anything – a Tarkalean hawk soaring through the sky, or a Filian python burrowing deep beneath the ground. He admits that he was never a very good shapeshifter, but believes he can be a good teacher. He promises once again that he will never treat the infant the way he was treated. Just then, Doctor Mora arrives and explains that he has heard about the infant and wants to help, much to Odo's dismay.
Mora admires the infant Changeling's size, and is surprised that Odo hasn't measured it. Barely hiding his annoyance at Mora's presence, Odo remarks that he thought Mora was on Earth helping Starfleet to develop new ways to detect Changeling infiltrators. With genuine concern, Mora asks how Odo is and reveals that he has been worried since the Founders removed Odo's shapeshifting abilities. As Mora picks up an instrument to start measuring the infant Odo reacts angrily, determined not to let Mora perform any experiments on it. Nevertheless determined to offer his advice, Mora suggests reducing the temperature to 17 degrees Celsius, at which the infant's morphogenic matrix will be most malleable. He adds that Odo could benefit from much of his knowledge, and begrudgingly Odo agrees to look at his reports. But Odo is still angry and resentful about the tests Mora subjected him to, a fact not lost on his old mentor. Mora states that he would be fascinated to observe Odo's less invasive approach to working with the infant, and determines to stay and observe.
In the birthing room, the midwife announces that Kira has been in labor too long and won't give birth today. It is obvious that Miles blames Shakaar because of his late arrival, but Kira asks Shakaar to stay around for a while.
Odo begins to introduce shapes to the infant, starting with a sphere. The infant remains motionless and in a gelatinous state but Odo persists, showing different shapes to it and talking about what they represent.
One week later, Mora expresses concern that the infant has barely increased in size and Odo seems to have made no progress in teaching it to assume other shapes. Their barely contained annoyance with each other finally boils over and they start to bicker. At the height of their argument they are interrupted by Captain Sisko, who reports that Starfleet Command is eager to establish communication with the infant as soon as possible. With little progress to date, Sisko warns that Starfleet may want to take over the project and asks that Odo file daily reports from now on. Drawing a comparison to the type of pressure he was placed under by the Cardassians when he was working on Odo during the Occupation, Mora suggests that they try some of his more invasive techniques on the infant.
With obvious reluctance, Odo places the infant into one of Mora's electrostatic devices – a circular shallow tank that carries a charge around the outside but no charge in the center. Mora insists that Odo initiate the charge, which he timidly does, and then that he increase it to a level at which the infant will feel discomfort. As Odo does so the infant begins to move for the first time, quickly sliding to the center to avoid the charge. Odo can't help but smile, and Mora reveals that he also smiled the first time Odo did that.
Kirayoshi O'Brien is bornIn Kira's bedroom, O'Brien massages her legs while Shakaar invites her to a zero-gravity tumbling performance on the Promenade. As the men squabble over the best way to relax her, Kira suddenly realizes that she's going back into labor.
Continuing to use Mora's electrostatic device, Odo is able to coax the infant into forming and holding shapes. He reveals to Mora that he used to not hold his shape on purpose in order to deny Mora the satisfaction of seeing it. Wistfully, Mora suggests that one day, if Odo is lucky, the infant may thank him for his efforts; on the other hand it may just leave, like Odo did. As they turn to leave the lab, the infant begins to form a shape, snaking up towards Odo and bending towards him. As Odo leans in to look closer, the infant forms a rough mirror of Odo's face. Odo and Mora are overcome with joy.
Returning to Odo's office, Odo and Mora are effervescent. Excitedly they chatter about the infant's shapeshifting. Mora suggests that in the coming days they begin to expose it to simple life forms, while Odo enthuses that he can't wait to communicate with it – there's so much he wants it to see, so much he wants to share. Mora compliments Odo on his approach of communicating with the infant, and admits that he was wrong. He can see that the infant is reaching out to Odo, is curious about him; the first time Odo did anything like that was when he formed a tentacle to slap Mora's hand away from the control panel of one of his devices. Mora admits that he was never able to form a connection with Odo, but Odo tells him that's not true. Odo suggests that he would still be nothing more than a lump of organic residue if it were not for Mora, and Mora is overcome. The two men have finally reached an understanding. As Mora turns to leave, Odo orders two glasses of champagne from the replicator so that they can celebrate.
Back in the birthing room, Kira is finally relaxed enough to give birth. Shakaar tries to keep Miles out of the way, but after missing his daughter Molly's birth Miles is determined not to miss this one. As they squabble, Kira tells them to leave.
In his darkened bar, Quark counts his profits on a PADD and mutters to himself that he'll have to start watering the drinks again. Startled by a noise, he notices Odo behind the bar setting out bottles and glasses. Doctor Mora, Odo says, has gone to sleep and he feels like celebrating, so he's buying Quark a drink. Initially skeptical at seeing Odo happy, Quark eventually comes round when Odo explains that finding the infant has changed his life; he has found a part of himself that he lost when he was forced to become a solid. Just then they are interrupted by the computer, which announces that it has detected biomimetic fluctuations in the infant.
As Odo rushes into the science lab, Mora explains that the infant's morphogenic matrix is destabilizing: it is dying. Odo is grief-stricken.
In the infirmary, Bashir speculates that the radiation must have damaged the infant's cytoplasm in a way they weren't able to detect. Mora suggests using an enzymatic induction to stabilize the biomimetic fluctuations. Odo waits outside.
Kira, utterly relaxed, finally nears delivery. Keiko invites Miles and Shakaar back into the room just in time to witness the birth of a baby boy.
Bashir emerges from the Infirmary and solemnly informs Odo that there was nothing they could do. Odo enters and takes the dying infant into his hands, begging it not to die. As he does so, it absorbs itself into his body and he stumbles backwards. Shocked, he walks towards the infirmary doors and then shapeshifts into a Tarkalean hawk, soaring up into the rafters of the Promenade and swooping over the upper level before coming to rest on one of the walkways. As he changes back into his normal self, his face is a mixture of joy and sorrow.
At one of the docking ports, Kira sees Shakaar onto a shuttle bound for Bajor. He invites her to take some leave and stay with him for a while, but she feels like staying aboard the station for a while.
Doctor Mora, also boarding the shuttle, tells Odo to think of the return of his shapeshifting abilities as a gift, something the infant wanted him to have. Odo admits that he finally understands what he must have meant to Mora, and vows to involve his mentor more in his life. They hug, and Mora departs.
Kira expresses her sorrow to Odo, and confides that she never wanted a baby but now just wants to hold him in her arms and never let go. Odo replies that he knows how she feels. Kira wraps her arm around her friend's shoulders and they walk slowly off together.