In this episode of Noll’s Nephew, we unpack the Catholic Church’s teaching on mortal sin—what it is, how it differs from venial sin, and why it matters for our salvation. Drawing on Scripture, the Catechism, and the words of the Church Fathers, we examine the three conditions for a sin to be mortal, its devastating effects on the soul, and the hope of forgiveness found in Confession. Far from being a message of fear, this teaching reveals God’s desire for us to live in grace and freedom. Mortal sin is deadly—but God’s mercy is greater.