'The Fosters' season 4 episode 17 spoilers update: Stef rescues teen prostitute; Noah Centineo discusses complicated character arc

Promotional image for "The Fosters" season 4.Facebook/thefostersTV

Stef (Teri Polo) works to save a teenage girl from a life of prostitution and violence in the upcoming episode of "The Fosters" season 4.

Titled "Diamond in the Rough," next week's episode will explore Stef's efforts to rescue a young girl from her pimp. According to the official synopsis, Stef begins a new assignment in human trafficking that leads her to Diamond a.k.a. Miranda Collins (Hope Olaide Wilson), a teenage girl who is turning tricks on the streets. Meanwhile, Callie's (Maia Mitchell) never-ending pursuit of justice starts to negatively affect her relationship with AJ (Tom Williamson).

Lena (Sherri Saum), on the other hand, must face the consequences after she conducted an off-campus LGBTQ sex education class for the students of Anchor Beach without the school administration's knowledge. Back at the Adams-Foster household, Jesus (Noah Centineo) is prescribed a special pair of glasses after his traumatic brain injury. Mariana (Cierra Ramirez) uses one of her school projects to cheer him up while he recovers.

Freeform released a new promo for the upcoming episode and it opens with Callie having a conversation with AJ. "Are you okay?" Callie asks her boyfriend. AJ sits beside her and explains he wants more quality time with her. Callie seeks advice from Mariana, who tells her foster sister that maybe AJ just needs some reassurance from her. The next scene cuts to Callie heading out to surprise AJ, only to catch him kissing another woman.

Jesus sustained a brain injury at the end of season 4A when he was punched by Nick (Louis Hunter). Aside from struggling with simple tasks like walking and talking, Jesus recently realized that he has lost the ability to read.

In an interview with Screener, Centineo said his preparation for Jesus' complicated story arc was "eye-opening but also super fun to do so much research to dive into a character." The actor said he watched documentaries, studies and went to physical therapy clinics to just observe. "A lot went into it and I hope I do it justice," he added.

The fourth season of "The Fosters" airs every Tuesday at 8 p.m. EDT on Freeform.

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