Speak to Morgan in Draynor Village. You will learn about his delima with his village being plaged by a vampire, who demands blood payments.
Accept the offer and head off to Harlow who is located in the Blue Moon inn, located in Varrock.
He will teach you, but for a price! He wants you to buy him a beer, so head on over to the bartender and buy a beer for 2gp. Now use the beer on Dr. Harlow and ask him how to kill vampires. You will learn that a stake is an essential tool for killing the vampire, or else he will regenerate his health. He will hand you a stake and then a stake hammer. He will then tell you that vampires are weakened when they smell garlic. He will then go through the instructions for killing the vampire.
Go back and speak to Morgan and ask him if he has any garlic. He said there should be some around. Go upstairs and search the dresser and you will then you will find some.
Now head north to the Draynor Manor and climb down the stairs in the eastern room. Open the coffin. You will atempt to kill the vampire but will fail. Now you have to fight it.
Once you kill him head back and tell Morgan. Congratulations! Quest Complete!