Plot line:
Amy is desparate. She obtains/steals an experimental aphrodisiac and erectile dysfunction drug from her lab.
She invites Sheldon over for dinner per obligations of the boyfriend-girlfriend agreement. Her plan is to spike the food and finally get Leonard to commit to an intimate relationship. But there is a complications. Leonard invites Leonard and Penny along to protect him from any possible advances that Amy has hinted at. (don't worry about grammar). Amy has already prepared the meal with the aphrodisiac laced into the main course. She can't back out or find a good excuse so they all eat the love potion. Leonard and Penny immediately feel the affects and excuse themselves, rushing back to Penny's appartment. Perhaps they don't even make it home using backseat of the car to succumb to the love potion.
Leonard is affected also. He has had a glass of wine at Leonard and Penny's insistence so he thinks it must be the wine talking, but he to is overcome by the drug and whisks a near fainting Amy off to bedroom for a long night of "coitus".
That night when Leonard and Penny make it home the love making continues and weakened by the drug Penny proposes to Leonard.
The aphrodisiac is only good for 4-6 hours ala Viagra. When the drug wares off Penny has decided she has made a big mistake.
In the meantime Sheldon is making excuses to go over to Amy's appartment and is continuing to get Amy into bed, making up rational excuses to continue having "coitus".
Penny gets together with Bernadette and Amy to discuss her conundrum, how to back out of the marriage proposal without breaking up with Leonard. Amy finally confesses to her machinations, and Penny now knows why she proposed, and is going to use the drugging as the perfect excuse to back out of the marriage proposal. But of course Sheldon can't find out. But of course he does. No one is good at keeping a secret. When Leonard tells Sheldon the marriage is off, Sheldon's curiousity is expressed in 20 questions that Leonard finally throws up his hands and tells him about the aphrodisiac laced meal.
Sheldon is furious. He marches over to Amy's appartment with Leonard and Penny in tow and confronts Amy with her deception and threatens to end the relationship, in scathing terms. Then Amy halts his attack with the fact that the drug wore off the night he ate the laced food. Everything after that was all Sheldon's doing. Sheldon now has to face his human frailty that is only meant to happen to the common people and not him. He sits on Amy's couch bewildered and simply ends with the phrase "Oh" .
