It was a toss-up for which was more mortifying: the presence of mistletoe over his head, in his library, or the idea that Gabe might think, given how William had offered him a seat right there beneath it, that this was a set-up. After all, how else would the mistletoe have gotten there? (How had the mistletoe gotten there?)
"It looks like ivy," he blurted out, before anything else more plausible came to mind. "There must be an infestation. Plants shouldn't be around books, they attract bugs, and bugs can eat parchment, so that will never do. I'll call Spencer right away." His eyes widened. "Not for..." Shit, he'd caught himself out on that one. "I mean, because it's ivy. Obviously. So not for anything else. He'll be able to get rid of it."
Just in case, however, he sent a flash-freezing charm toward the ceiling. Not the best choice for plant obliteration, because if anything went wrong and it melted, he might have water near the books, but flame was an even worse option, so he couldn't just char the thing into ashes before Gabe got a good look at it. Hopefully the ice would obscure his view.
"We should probably close the library," he added, because apparently he couldn't stop talking for long enough to think clearly. "It got in here somehow, after all, it might be cursed. I don't know anything about plants, it might be poison ivy. Or venomous ivy. Spencer will know. Because he teaches Herbology." Shut up, shut up. He bit his lower lip to keep himself from saying anything else, pointed to the door, and looked at Gabe as earnestly as possible while possibly having a minor panic attack.