Potions has never been Lily's favorite subject but she's always been really good at it. A project that determines whether she passes or fails seems like no big deal to her, until she realizes her partner is James Potter. The potion works except for one thing: they can't reverse it. Lily and James are trapped in the other's body, and if they ask for help, they'll fail. They have to fool everyone unil they fix it! This is the story of how they almost failed 7th year Potions, but fell in love instead!

They know they have to work together to solve this problem, but asking Lily and James to get along is like asking a very hungry lion not to eat you... it's just not going to happen. Lily and James decide that they can do this on their own, which only causes more problems as they try to outdo the other in embarrassing the person they're supposed to be. Some very interesting consequences...

Lily and James get to work on finding the solution, but when they find the answer, they're not as happy as they thought they would be. James has to do something for Lily now, which is be nice to what is ultimately his competition for Lily's affections, while Lily, meanwhile, finds out that part of being James Potter is playing Quidditch...

Lily and James are really busy, what with flying lessons, arguments, learning to be the other, arguments, creating the potion, and more arguments! In addition to all this, it's time to deal with Snivellus. Will Lily and James be able to act like the other around the Slytherin of most dispute between them?

Lily learns that it's hard to be an animagus, and that there's more the the Marauders than she always assumed. James gets to date from the other side of the equation, and gets more than he bargained for. And Lily and James find themselves tangled in a web of confusing and conflicting emotions...

They've fallen in love, but what will their potions grade be? And how will Slughorn react...