"Ten Days in the Valley" follows Jane Sadler (Sedgwick), an overworked television producer and single mother in the middle of a fractious separation. When her young daughter goes missing in the middle of the night, Jane's world - and her controversial police series - implodes. Life imitates art: everything's a mystery, everyone has a secret, and no one can be trusted.
After her award-winning documentary brings down the San Diego Police Department, Jane takes her storytelling talents to the fictional world with a television cop drama. But the pressures and stress of balancing her career with being a devoted mom start to take their toll on Jane. When her daughter, Lake (Abigail Pniowsky), goes missing, and the Los Angeles Police Department starts to investigate, Jane's world only gets more difficult.
Everyone in Jane's life suddenly becomes suspicious. Pete (Kick Gurry), Jane's ex, is the number one suspect at the start of the case. He is a charismatic, unpredictable music producer and a recovering heroin addict seeking joint custody of Lake. Ali (Erika Christensen), Jane's younger sister, is a capable and pragmatic rock of stability and support during Jane's ongoing ordeal, who can't help but question many of Jane's choices. Ali and her husband, Tom (Josh Radall), are trying to conceive their own, but her priorities take a back seat when Lake goes missing. Tom is a decisively tough yet warm partner to Ali, an ambitious journalist who sees it all. On Jane's television series, her right-hand man is Matt (Malcolm-Jamal Warner). Matt is a strong-headed writer and co-executive producer, but he is desperate to have his own series one day and can never seem to meet Jane's expectations.
Outside of Jane's family are the police officers from the LAPD. Detective Bird (Adewale Akinnuoye-Agbaje), Robbery Homicide Division, takes on Jane's case. A strategically non-judgmental maverick investigator, Bird serves as the lead detective investigating the disappearance of Jane's daughter. Bird answers to Commander Gomez (Felix Solas), who presides over the important LAPD Detective Bureau with the decisiveness and confidence of an oligarch. Gomez's overall goal is to clean up the image of the LAPD, and he is struggling to make that happen with all the cop dramas on TV, including Jane's. And there is also the source of Jane's stories -- Gus (Francois Battiste). Gus is a narcotics detective who serves as Jane's confidante and secret source for her show.