The Fosters is a compelling, one-hour drama about a multi-ethnic family mix of foster and biological kids being raised by two moms. Stef Foster (Teri Polo), a dedicated police officer, and her partner Lena Foster (Sherri Saum), a school Vice Principal, have built a close-knit, loving family with Stef's biological son from a previous marriage, Brandon (David Lambert), and their adopted twins, Mariana (Cierra Ramirez) and Jesus (Jake T. Austin). Their lives are disrupted in unexpected ways when Lena meets Callie (Maia Mitchell), a hardened teen with an abusive past who has spent her life in and out of foster homes. Lena and Stef warily welcome Callie into their home thinking it's just for a few weeks, until a more permanent placement can be found.

Callie is quick to observe that the Fosters are an atypical family, and her blunt commentary hits a nerve with Jesus and Mariana who are struggling with their own identities. The twins have the opportunity to meet their birth mother, but they aren't sure if they are emotionally ready, or if they want to share the experience with their adoptive moms. Callie also discovers that Mariana is harboring a secret that could land her in serious trouble.

Brandon, a talented musician with a kind soul, lends Callie a hand in navigating the classrooms and social scene at the Fosters' high school, Anchor Beach Community Charter School. He's faced with a tough decision when Callie decides to ditch school to reconnect with someone from her past. What happens next will determine if Stef and Lena made the right choice in taking a chance on Callie, and whether they have room in their home - and their hearts - for one more.

The new season picks up immediately from the dramatic cliffhanger finale with Mariana's emotionally devastated boyfriend Nick bringing a gun to school. Now that Callie's moms know she slept with Brandon, Callie worries they may not want her to remain part of the family.