Jenny and Tyrese are fixing the junction box but they don't know what switches to flip.
If you talk to Jenny they ask you to help them in the flipping. If you get to turn off all of the lights Jenny and Tyrese would leave.
This is the low-spoiler guide for "Flipping the switches" puzzle in The Darkside Detective - A Fumble in the Dark. Unlike in normal walkthrough, you get gradual hints on how to solve the puzzle. Click the big button below to see your first hint. If the hint contains a spoiler, you will be warned about it before clicking.