It's wrong to sleep with your friend's parent.
Diego and his friend Thom are both drinking whiskey with his mom, Monica, who begins to flirt with Thom, and Diego feels uneasy.
Thom wants to react to Monica's advances.
Thom decides to ignore Monica's flirting and asks Diego to go outside to hang out instead.
Thom flirts back with Monica who then invites him into her bedroom where they have sex.
Diego is happy that his friend didn't betray their friendship, but remains angry with Monica.
Diego is angry at both Thom and Monica because he feels weird about the whole thing.