Dateline: Unforgettable Season 4

A chance encounter on the Pacific Coast Highway with a woman he first spoke to in a jail cell leads Keith Morrison to re-examine the mysterious death of Las Vegas casino magnate Ted Binion.

When Dr. Joe Sonnier is murdered in Lubbock, TX, the investigation reveals simmering jealousies and a love triangle; Andrea Canning recalls a doctor who dedicated his life to helping others.

A pastor's secrets come to light, triggering a murder investigation; Josh Mankiewicz looks back at a case that shattered a congregation and exposed the cost of their trust.

When a woman is found dead in her SUV, the investigation into her murder reveals a tangled web of sex and lies. Dennis Murphy looks back on his unusual interview with the lead suspect.

Chris Smith's family receives an email stating that he is leaving California to surf the world; months later, they wonder if he really left. Keith Morrison offers new insights into the case.

After 24-year-old Lisa Zeigert is killed in Agawam, MA, in 1992, her family keeps the case in the public eye for decades and it was featured on the show Unsolved Mysteries; Andrea Canning reflects on the harrowing mystery and discusses the inspiration she's drawn from Lisa's loved ones.

In Los Angeles, newlywed Sherri Rasmussen is killed in an apparent botched burglary in February 1986; nearly 20 years later, a detective discovers a clue that turns the case on its head; Josh Mankiewicz revisits a story with a twist that surprised him.

To many, it seemed like a romance between a former football player and homecoming queen; but when it ends in death, the police investigate; Dennis Murphy reflects on a secret relationship that led a churchgoing couple down a dangerous path.

A bombshell more than a decade after the crime reignites the investigation into the death of Sarah Pagel's mother. Andrea Canning looks back at her emotional interview with Sarah, whose mom touched so many lives.