A bipolar bigoted junkie cop, manipulates and hallucinates his way through the festive season in a bid to secure promotion and win back his wife and daughter. 改编自《猜火车》作者埃文·威尔什的同名小说。《污垢》讲述了一个发生在爱丁堡邪恶警察身上的故事。该警察脾气暴虐，作恶多端，而且还涉及未成年人的xing交易。