Severus with grief and madness tries to resurrect Lily by preforming a ritual over where she and James are buried but for some reason it doesn’t take to her, Severus leaves distraught and his sanity slowly coming back to him to only hear the next morning about how the Potters grave had been dug up so he goes to check and sure enough there’s only one casket in the ground closed and one that’s literally BROKEN open. He then tried to search the era looking for Lily to only come across a Frankenstein zombie wendigo esc James fucking potter who is hardly cognitive. The story then takes full place as Severus hides the fact that he 1. Managed to be the first person in wizarding history to successfully reanimate a body and 2. Has James fucking Potter in his house, along with trying to get James to remember who he is. Slowly James comes back to being himself but not to a full completion, being able to only speak in few words, and apologizes for going too far sometimes with bullying Severus and Severus shrugging it off, joking even that James would never say that. Slowly they find comfort in each other and develop a relationship where they are both bonded over the loss of a loved one, being seen as a monster by the world, and only being able to be themselves in each others company.
Lupin and Sirius side quest during all of this trying to find out who tf stole James Potters body and then finding out Severus has him and then trying to get Severus in trouble for resurrection AND use James to confirm Sirius did and fact not kill him and his wife.
The ending being a conflated amount of emotions of grief, figuring out of James should be kept alive or be killed (again), and the loss of not only your friends due to death, but due to betrayal (Peter).
I just love black magic Snape and making the marauders infight and turn against each other.
Bonus: James plowing Severus during hate sex telling how Lily could never give Severus pleasure like this and Severus clapping back with “Lily could never give you life like this.” Covered in dirt and mud from rain or something idk. Talk amongst yourselves.