Over the next two hours of testing, Mr. Labi's mood went from slight anger ("All right, all right, if you insist on making me do this, let's waste some more time here!") to bewildered suspicion as he held the detector and looked at Brian ("Is this thing broken? Why isn't there any reaction at all? Sir, could you be a Squib?"),
then progressed to self-doubt ("Damn it, you really didn't use any offensive magic. That can't be right-so this Lucius really was stupid enough to get knocked out by a Muggle's punch? No-no, I know! He must have noticed me patrolling overhead,
then deliberately knocked himself unconscious so he could use me to... Looks like I'll have to test his wand"),
and finally, when he saw a projection spell showing a snake-shaped seal emerge from Lucius's wand, his expression changed dramatically, and he was overjoyed ("This is-well, well! Ahem, since the tests haven't turned up any problems with you, you can leave. I have an urgent matter to handle. Leave Lucius to me-right, don't look at me like that. All I can tell you is that this fellow is in serious trouble!").
Even without Labi saying anything, everyone could see that there was definitely something wrong with that snake emblem. While Labi was pulling a black sack over Lucius's head, Arthur considerately leaned his head over and said in a very quiet voice:
"Everyone, that snake emblem is a secret sign devised by a gang of black market merchants who have been moving around Diagon Alley lately. The Improper Use of Magic Office has been investigating it recently. Ha, Lucius! I was wondering why he'd turned up alone in Diagon Alley out of nowhere. Now we're in for a good show!"
Although it was rather ironic, ordinary Ministry of Magic