FBI Files features dramatic reconstructions and interviews with agents who participated, the series looks back at some of the FBI's most sensational cases continues.

The Deadly Dentist  tells the story of an amiable family practitioner who was also a serial killer. On January 14, 1980, 50-year-old Sophie Barrera was killed when a bomb attached to the underside of her car exploded. Her son Frederick pointed the authorities in the direction of Glennon Engleman, against whom Sophie had filed a civil suit for $14,000. 

The apparently kindly dentist was an unlikely suspect, but his ex-wife Ruth painted a very different picture, telling FBI Agent William McGarvey that Engleman was responsible for seven murders. Although the details were sketchy, her story seemed to check out. 

Further investigation revealed that a number of people connected to Engleman had met with tragedy, with Engleman and his business partners profiting on each occasion. After Ruth agreed to have her condo wired, she finally managed to get her ex-husband to say what McGarvey wanted to hear. 

The FBI man now had sufficient evidence, and the extent of Engleman's crimes was revealed in court in August 1980. The jury took just 12 hours to find him guilty. Engleman would spend the rest of his life in prison before his death in 1999.

The Deadly Dentist is told over two parts, Monday 11 May and Tuesday 12 May at 9pm on PBS America