Joan, Adam, and Grace are at Joan's kitchen table, working on their test. There's a pile of twigs, one of which is commanding Adam's attention. Grace is lighting matches. Joan asks what to do first. Grace: "Ask your brother for the answer." Joan blows out the match, saying, "To be humble, you have to be proud." Adam: "Wait, aren't those opposites?" Luke comes downstairs, and Grace stage-whispers, "Ask him. Ask him, ask him!" Joan refuses and asks if there's a chemical formula for twigs. Luke shakes his head to himself as he gets something out of the fridge. Adam: "Cellulose is C6-H12-O6." Joan makes no effort to conceal her astonishment. Adam explains, "Uh, I have an eidetic memory." Joan: "What's that?" Luke: "Photographic." Grace looks at Adam: "He can barely remember his name." Adam says that he knows a lot of stuff, but he just can't put it together. Joan asks for the chemical equation for fire. Grace: "Wood doesn't actually burn." Joan says that's insane as she blows out another match Grace has lit. Grace continues, "What burns is the gas released when the wood gets hot. Therefore the reaction would have to be gasification through oxidation reduction, then combustion." She's got Luke's attention away from his chocolate milk now: "It is so hot that you know that." Hee. Grace just glares. Adam asks Grace, "Dude, are you smart?" Grace: "Just because I rebuke the whole 'formal schooling equals knowledge' crap doesn't mean I'm stupid." In the background, Luke is struggling openly to try to get the lid off a jar of cookies. Joan asks, "So what about gas?" She looks at Adam, who says, "Chah, like I know." Grace: "And Rain Man's back to underpants." I love this show, in case it isn't already obvious. Adam says, "Listen, you tell me the formula and I'll tell you the substance, or..." Luke is still getting a hernia trying to open the cookie jar, and his grunting attracts Grace's attention. She snaps her fingers and gestures to Luke. He looks sheepish, but brings her the jar. Adam says if they tell him the substance, he can tell them the formula. Joan says to work it backwards. As Grace opens the cookie jar for Luke, Joan looks at her brother like he's a reject. Grace says, "Charcoal plus the mystery gas equals wood plus oxygen and heat." Adam: "C50-H10-O plus10CH20. That's formaldehyde...equals oxidized and reduced C6-H12-O6." Grace commands Joan to start scribbling. Joan asks what that means. Luke nods to himself. Grace grabs her bag and leaves, saying it means they're done. Joan asks Luke if they got it right. He replies, "It's like watching three monkeys build a particle accelerator using tinfoil and a BB gun."