Billy was helping to train the new police intake. Billy had been introduced by Dignum to the group as a hardened ex villain and in a sarcastic quip, not one who was a petty thief so their stuff would be safe.
Someone in charge of in-house training had had the bright idea of setting up a course on how, supposedly, to do undercover work. After Dignum's slanderous introduction Billy always had to playact being the chief villain. As Billy had had Costello, and also Mr French, as a teacher the sessions were not short on variety and drama, especially when Billy used a boot on certain knuckle heads who thought that acting tough and verbally stupid would let them pass muster. The trainer seconded from the nearby Police Academy had objected to this; Billy "took" him into a private location and told him about the who and why of the boot. The trainer backed down, but wasn't very happy. Then the trainer had objected when Billy "shot" an involved bystander for no reason at all. Billy immediately enlightened him, and the class, on what being Mr French's assistant entailed. Billy was not a popular instructor with the rookies, or anyone else since he tended to represent reality, red in tooth and claw, over theory. On the other hand, he was increasingly respected and feared, and not just by the other rank and file cops.
Billy had also been told to attend some sessions on criminal psychology and mental issues; Queenan had thought it a good idea, something about know thyself. Madolyn had been giving the sessions. Naturally she had seen him and wanted answers. Billy tried to avoid her, but eventually she caught up with him and demanded to know what he was doing there. Billy said that he had never lied to her, but he could not tell her the truth either. For now she should just accept what everyone else did, that he was a police informer who had been flushed out and had done a deal with the police for protection. One day he would tell her the truth. This just served to get Madolyn's interest charged up, she decided to investigate further.
Billy had just given a painful (to the student) demonstration on how not to use a knife on himself when Brown arrived and signalled him, saying "Ellerby says go find either Queenan or Dignum now. There are some FBI officers after you, you know why". So, crunch time.