Trust Me (Or, An Embarrassing Ritual with Unexpected Side-effects) (слэш)

Severus Snape is tired of everything. So tired, in fact, that he is considering extinguishing his own life – it is, he suspects, the only way he'll ever get some rest. But when he discovers that Harry Potter is joining the staff of Hogwarts, he realises that his task – to prevent Potter from causing further mayhem and destruction – is not yet done, and so he decides to postpone his eternal sleep for a little while longer . . . with 'interesting' results!