B'Elanna Torres is in a good mood, until she arrives at work in Engineering and almost faints. Icheb scans her and panics when he thinks she has a parasite within her. Seven of Nine also scans Torres and comes up with a different diagnosis: B'Elanna is pregnant.
The Doctor confirms Seven's diagnosis. The fetus is seven weeks old, and perfectly healthy, except for a genetic defect that causes abnormal spine curvature in Klingon females. B'Elanna, who is half Klingon, had surgery as a baby to correct this defect. The Doctor says that nowadays genetic resequencing is the preferred treatment and that he can perform the procedure the following day. He also shows Tom Paris and B'Elanna a holographic projection of what their daughter will look like. Tom thinks she is beautiful but B'Elanna is distressed to learn her daughter will have Klingon facial ridges.
During the procedure the next day, B'Elanna reminisces back to her childhood as a Klingon girl on the colony in which she grew up. She blames herself, especially her Klingon half, for her human father leaving her, and resolves to not let the same happen to her daughter. She proposes further genetic resequencing to delete various Klingon genes, but the Doctor and B'Elanna's husband Tom Paris disagree.
During one of the couple's arguments, Torres mentions Voyager has 140 humans on board. This is not intended as a full crew count as other aliens, such as Vulcans, Bolians and Bajorans are also part of the crew.
When the Doctor suddenly changes his mind, Tom seeks a second opinion from Icheb (his aptitude for genetics was first referenced in "Child's Play"). Icheb disagrees with the Doctor's new assessment and discovers that the EMH's program has been tampered with. Tom stops the procedure in the nick of time, and he and B'Elanna have an argument. She tearfully admits what she fears will happen to her daughter; that Paris will leave them like her father left her, and Tom reaffirms his commitment to his growing family. B'Elanna asks the Doctor to be the godfather.