WATCH HERE: 5-part Oakland County Child Killer docuseries

The "Child Killer" docuseries focuses on the unsolved murders of at least four children in Oakland County between 1976 and 1977.

Investigators have been working for decades to determine who the serial killer is and if he is still alive. Those who knew the victims -- their families, friends, classmates, teachers, coaches and neighbors -- have been forever changed by what happened during the 13-month period from February 1976 to March 1977. In that time, the four children were abducted and murdered with their bodies left in various locations within or just outside Oakland County.

There were at least two other murder cases that investigators believe may have been victims of the "Oakland County Child Killer" or "The Babysitter Killer," as some called him.

The ensuing murder investigation was the largest of its kind in U.S. history at the time.

Here are the five parts to the docuseries:

• Chapter 1: North Fox Island
• Chapter 2: Out in the cold
• Chapter 3: Timmy King
• Chapter 4: The investigation
• Chapter 5: Suspicion

You may also watch the five parts here:

Chapter 1: North Fox Island

Chapter 2: Out in the cold

Chapter 3: Timmy King

Chapter 4: The investigation

Chapter 5: Suspicion

Tip line

Anyone with information on this case should contact investigators at 833-784-9425.