Married podcasters discover their plumber is a serial killer, join forces in twisted partnership

Peacock's "Based on a True Story" season finale contains spoilers for the entire first season.
Ava and Nathan partner with part-time plumber and part-time serial killer Matt to document his Westside Ripper crimes for a podcast.
Matt indoctrinates Ava and Nathan into his world by killing their friend Ruby and dumping her body on their doorstep.
Ava and Nathan bury Ruby's body in a tennis court pit, but forget to lock the front door and are caught by Ruby's husband.
Matt wants to bring Ava and Nathan into his world and attach himself to them, leaving them with literal blood on their hands to silence them.