Basically, Captain Jack has a pretty wife. However, Professor Snape covets his wife, and has Jack sent away to prison. He gets out of prison, comes back, and finds out that his wife is gone, after "something happened. Something not very nice." So, he goes for revenge. Bellatrix had a thing for Jack before he was sent away, and still wants him. So together, they team up to get back at Snape, who is caring for Jack's daughter. She's now in her late teens, and Snape plans to marry her! In the meantime, there are meat pies. Shepherd's pie, even. Peppered with pieces of actual shepherd on top.