This is another Snape/Harry story, something I'm still really craving.
Backstory; When Severus joins the Order he is pleasantly surprised to find James has grown up, and isn't the obnoxious self-entitled brat he once was. They even start to like each other, though they keep it from Dumbledore. They both know the elder wizard would use it as emotional blackmail, especially against Severus.
James searches high and low for a way to protect baby Harry, and ends up asking Severus for a huge favor; a blood magic ritual. This ritual binds Harry and Severus through blood, and as long as they both live, neither can die from unnatural causes. This, and not his mother's love, is what saves Harry.
Fast forward to Harry's 6th year. After Ron is cured of the love potion, both boys drink the poisoned brandy. While Ron is convulsing on the floor, Harry's scar throbs and bleeds. He's able to save his friend despite the pain, but can't help but wonder why he wasn't affected in the same way.
Shortly after he accompanies Ron to the Hospital Wing, Dumbledore brings Snape in. Snape had been in Dumbledore's office when he inexplicably began to convulse; blood spilling from a strange wound on his hand.
Dumbledore realizes what happened, and so Harry learns the truth. When Snape wakes up Harry demands to know the truth. At first they start to like each other, but then they fall in love, while keeping their relationship a secret of course.
I will play either character.