The Family of the Vourdalak
I only read this quite recently, although I have it in several collections. It's a very unsettling story. A father goes off, hunting a Turkish bandit. He tells his family that if he hasn't returned within 10 days to assume him dead. If he comes back after 10 days then they are on no account to let him in, for he will have become a vourdalak - a vampire. Luckily for us, they don't do as they are told. Creepy. Very, very creep.