Here's the summary from their website:
On January 13, 1999, a girl named Hae Min Lee, a senior at Woodlawn High School in Baltimore County, Maryland, disappeared. A month later, her body turned up in a city park. She'd been strangled. Her 17-year-old ex-boyfriend, Adnan Syed, was arrested for the crime, and within a year, he was convicted and sentenced to spend the rest of his life in prison.
The case against him was largely based on the story of one witness, Adnan’s friend Jay, who testified that he helped Adnan bury Hae's body. But Adnan has always maintained he had nothing to do with Hae’s death. Some people believe he’s telling the truth. Many others don’t.
Over the season, she recounts facts, analyzes transcripts, talks to experts, finds and interviews old friends and witnesses, visits the crime scenes, and challenges Adnan's side of the story through frequent phone calls from the jail where he is serving a life sentence.
Who is lying? Who is telling the truth? And really - how can you tell? Can you ever really know what someone is truly capable of?