Spoilers about how you are possibly recruited into the Dark Brotherhood: Upon visiting a boy in Windhelm, he offers you a contract. The contract has you going to an orphanage to kill a vicious lady who hits the children and prevents them from being adopted. The orphanage is located in The Rift. Upon arriving there, the player sees how the woman is berating the children and then stalks her until they are both alone. He kills her. After that, he notices that the children find out and they all start to laugh / applaud (one even commends the Dark Brotherhood). After that quest is finished, you’ll receive a note from the Dark Brotherhood given to you by a courier.