Blackwater Lane

Cass Anderson finishes her class and talks with a student about personal life. On a country road in heavy rain, she notices a car with a lone female passenger and keeps driving home, unsettled by the glimpse but deciding to continue.

The next morning, Matthew tells Cass that a woman's body was found on Blackwater Lane. Cass realizes she drove that road the night before, which sows guilt and fear as a homicide investigation unfolds.

Cass meets her friend Rachel, who skews toward stirring gossip and claims John still fancies Cass. They discuss theatre, Cass's future, and whether she and Matthew will start a family, revealing strains in their circle.

A stranger lurks in Cass's garden, and later at a party Rachel mentions Jane Walters' work connection, hinting at a past conflict. Cass recalls having seen Jane before, tying Jane’s fate to her own circle.

Cass keeps getting silent phone calls and senses a ghostly presence. At the site where Jane died, she finds Jane's ring, heightening the sense that the murder directly implicates her life.

The police interview Cass and she admits she saw Jane the night she died, but didn't realize Jane was dead. The cops reveal they know Cass traveled Blackwater Lane, amplifying her anxiety and paranoia.

Back at home, Matt leaves for work and Cass searches for Mary, but finds no plan. She experiences nightmare hauntings, feeling choked and haunted by images of her dead mother, escalating her sense of danger.

Matt takes Cass to a mental health professional who warns of probable early dementia due to stress. Soon after, Cass sees her mother's face on a TV broadcast, driving her deeper into trauma and confusion.

Cass ends up in the hospital after a drug overdose, underscoring how far her mental state has deteriorated. A detective-side session reveals her inheritance tied to the 'Crawford house', connecting Rachel’s family history to her apparent wealth.

An old friend reveals that Rachel had an affair with a coworker's husband and that Cass may have signed documents she doesn't recall. The disclosures sow doubt about Rachel and Matt, intensifying Cass's confusion and fear.

Cass is targeted by an apparent attempt to run her off the road, prompting the cops to revisit a past incident. They reveal a second security contract that Cass did not know about, adding another layer of secrecy.

Clues emerge pointing to Rachel’s motive tied to Jane's knowledge of an affair. Cass suspects Rachel killed Jane to prevent exposure, and the couple's manipulation of Cass deepens as the truth remains buried. The tension mounts as Cass realizes she might be framed.

Rachel and Matt corner Cass, restraining and attempting to control her. Rachel then admits they staged her breakdown as revenge for the past humiliation; the manipulation culminates in a brutal confession about Jane’s murder.

In the final twist, Rachel stabs Matt in a bid for control, finally revealing that she orchestrated Cass's torment and was responsible for Jane's murder. Cass's nightmare ends only as Rachel's guilt erupts.