Bob's field of vision was suddenly filled with a variety of flashing, colored lights. Stupid proximity alarm charm failing to go off until Beckett was too close for Bob to do anything about hiding any incriminating evidence. Really, Bob needed to see about modifying the charm to alert him sooner, but this was the best he'd been able to do when it came to modifying a sound-based alarm to a light-based one on short notice. Clearly Bob's fault for trying to respect (some of) the rules and stay quiet in the library by making it so that the curse magic in Beckett would cause him to light up and—
Wait a second.
"Beckett, what the hell is wrong with your arm?" Bob demanded, shielding his eyes against the brilliant light shining through the long sleeves of Beckett's robes. "Did you do something? I fucking told you to leave it alone, you don't know what might trigger this—" Bob growled, grabbing for the librarian's arm. This was way more important than figuring out a working class schedule for Ancient Runes.