"48 HOURS" CRIME TIME DOUBLE FEATURE: MURDERERS TRACKED BY THEIR OWN WORDS

Back-to-Back Encore Episodes All Summer

Saturday, Aug. 17

9:00 PM, ET/PT - Just over a decade after Mark Twitchell was convicted of murdering Johnny Altinger, who prosecutors say was lured into a garage, stabbed and dismembered, 48 HOURS contributor Troy Roberts gets a rare look inside Twitchell's mind through his writings, in an encore of "The Dexter Killer," to be broadcast Saturday, Aug. 17 (9:00 PM, ET/PT) on the CBS Television Network and streamed on Paramount+. 48 HOURS and Roberts have been covering Twitchell's case since 2011. In this broadcast, investigative journalist and author Steve Lillebuen reveals letters he exchanged with Twitchell over three years. Watch a preview.

10:00 PM, ET/PT - Bart and Krista Halderson had a beautiful home in Windsor, Wis., and two adult sons they adored, so when Bart and Krista suddenly disappeared in July 2021, it stunned their community. 48 HOURS correspondent Erin Moriarty reports on how information found on social media would lead investigators to their killer in an encore of "The Snapchat Clue," to be broadcast Saturday, Aug. 17 (10:00 PM, ET/PT) on the CBS Television Network and streaming on Paramount+. Mystery surrounded the couple's disappearance, and investigators immediately turned to family members for information, including sons Mitchell, who worked in tech, and Chandler, then a college student living at home. Chandler said he was excited about a new job offer he said he had with Elon Musk's SpaceX. Chandler told police his parents had gone to the family cabin for the July 4 holiday weekend and never returned. Then, police would finally find a clue in the most unlikely place - the social media app Snapchat. Watch a preview.

Judy Tygard is the executive producer of 48 HOURS, which is broadcast Saturday nights and streams anytime on Paramount+. You can also watch 48 HOURS on CBS News 24/7. 48 HOURS is also available on CBSNews.com, Pluto US, Pluto UK, Pluto Nordics, Pluto Canada and Pluto South Africa. Download the CBS News app on your phone or connected TV. Follow 48 HOURS on X, Facebook and Instagram. Listen to podcasts at CBS Audio.