Basic Trope: A virgin, usually a woman, is required to be the subject of a Human Sacrifice
Straight: Sarah, a virgin, is kidnapped by the evil Cult of D'yatghra to be used as a sacrifice to their evil god.
Sarah has been groomed since birth by her parents to be a sacrifice; this includes steering her away from temptation and making sure no one... interferes with her virginity, by the simple expedience of ensuring that she never comes close enough to anyone to even touch them.
The cult requires the blood of a virgin... but not all of it. Meaning Sarah gets to have her blood shed for their dark god over and over again.
A virgin sacrifice is needed. Unfortunately, the cult can't actually find a virgin, so they have to make do with Sarah, who isn't one. Sarah doesn't appreciate the insinuations and snide comments that she's been around the block a few times.