At first, John thought he was lying. That he was making shit up to get out of taking his trig test. Trying to argue the point when he felt like a grenade had exploded inside his head had just led to him puking all over his bedsheets, which had not pleased John in the least. He'd actually grabbed Dean's arm and tried to haul him up out of bed until Dean screamed bloody murder and almost passed out. Even then, all he did was give Dean aspirin and instructions to sleep it off.

36 hours later, when Dean's still panting in agony from the relentless, excruciating pain, John admits that something is probably wrong. He tells Dean that if he doesn't feel better by morning, they're going to the hospital. By dawn, the pain has backed off to a manageable (well, for a Winchester) level and he can stand normal sounds and indirect sunlight. He eats dinner that evening for the first time in three days and goes to school the next day to make up his math test.

A month later, he's in trig when the headache starts. He tries to ignore it, just get through the last two periods of the day, but the pain gets so bad during gym class that he can barely make it into the nurse's office. She gives him Excedrin and lets him spend the last hour of the day in a dark, quiet back room. Driving home is misery; by the time he picks Sam up from junior high and gets the both of them home he's ready to load his Glock and put an end to the goddamn headache once and for all, but he doesn't have the energy or focus to do it. He closes all the curtains in the house and makes Sam swear on pain of death to stay the hell away from him. The headache doesn't last as long this time--it's gone by noon the next day--but 24 hours is still 23 hours and 59 minutes too long. Plus, he misses another trig test and has to make it up the next day.

The third time it happens, he finally puts the pieces together. Somehow his headaches are connected to his math tests. He calls a clinic with a fake story about a college paper and finds out that chronic severe headaches are called migraines and they can be triggered by physical things, like certain foods or environmental factors, or emotional stress. Bingo.

"You're trying to tell me you're allergic to trigonometry?" John sputters.

"Sort of," replies Dean. "It's not like I'll ever need to know it anyway. Can't I just get a doctor's note that I don't have to take it?"

"You come up with the money to see a doctor, you can do whatever you want."

He starts with his math teacher, laying out the situation and asking if he could take the tests open-book. Shockingly, Mr. Laudermilch actually goes for it. "My wife has had migraines since I met her," the teacher explains. "I know how agonizing they can be. If you continue to attend class regularly and turn in your homework on time, I'll allow you to use one 5 by 7 inch index card of notes during the test."

It actually works. He makes it through the rest of the school year without another migraine and also improves his trig grade a few points. It isn't until late April, when John stumbles in after a hunt with a four-inch chunk missing from his arm, that Dean gets another migraine. However, Sam takes pity on him and walks two miles to the drugstore to get him Excedrin and a few chemical heat packs. He's still laid up for two days, but now that he understands what's going on a little better, he can take care of himself.

That doesn't stop him from burning his trig book on the last day of school, though.