Bree, a 17-year old high school student who was conceived through anonymous donor sperm, discovers she has at least 15 half-siblings around the world and embarks on a quest to connect with them and possibly find her donor.

Bree visits the Cryobank in California with her half-siblings, Jesse and Jayme, to submit an official request to contact their sperm donor. In Boston, Jesse B. helps Bree discover crucial information about their donor.

In Boston, Bree bonds with her half-sisters, Paige and Molly, who have deeply unresolved feelings about being donor-conceived. Paige and Molly help Bree forge a major breakthrough in her search for their sperm donor.

The donor families gather for a reunion in Lake Tahoe and Bree and her half-siblings, Jonah, Paige, and Molly, disclose what they've learned about their sperm donor to the rest of the group.

Bree shares the news that she finally received a response back from the sperm donor. But this new communication forces Bree to question where exactly the sperm donor fits in her life.