The Captain has been working for three consecutive days. Right now, it's the late tour from 4pm until 8am. The elections had meant he'd needed to be on duty, so that's what he was doing, but he was going to have a quick nap on the couch in his office first... The precinct's patrolmen were guarding the polls during the election, so when relieving  another patrolman guarding the polls one night, they notice that one of the streetlights is out, they realise it has been happening a lot during the polls, so maybe it isn't a coincidence.