Their father's stern command echoes in their minds, "You mustn't move!" But it's impossible to resist as their bodies betray them, their innate lubrication soaking the hard cocks they've both been craving. The siblings lick and envelop each other's penises hungrily, their tight, untouched vaginas clenching around the invading shafts. Their taboo lust consumes them, and they collapse into a post-coital mix of remorse and shame, their bodies slick with spent fluids, praying for absolution from their sinful desires.