Investigation Discovery’s Evil Lives Here: The Killer Speaks returns Sunday with a story that cuts to the bone of sibling loyalty and betrayal. Airing at 9 PM ET, A True Act of Evil (Season 2, Episode 6) centers on Kristin and Brandon, a pair of foster kids whose shared history makes his eventual transformation into a killer all the more devastating.

The series, now in its second season, has made a name for itself by bringing viewers inside the homes of murderers—not just figuratively, but literally, through interviews with family members still grappling with the ripple effects of violence and deceit. This week’s episode focuses squarely on Kristin’s struggle to understand how her brother, once her closest confidant, became capable of taking a life.

Expect raw, emotional interviews and difficult questions as Kristin searches for answers—and as the series itself continues its grim project of trying to make sense of the senseless. Like other installments, A True Act of Evil also features conversations with Brandon from prison, allowing the killer’s perspective to weave through the narrative.

Evil Lives Here: The Killer Speaks airs Sunday at 9:00pm ET on Investigation Discovery.