Locate and Access Internal Leak

What happens here

Inside the house, the smoke test quickly identifies the source of the sewer smell: smoke is seen clearly escaping from a light fixture in a bathroom ceiling. To gain access to the faulty plumbing and begin repairs, a reciprocating saw is used to carefully cut a rectangular opening in the drywall ceiling directly above the light fixture.

Goal: Visually pinpoint the exact location of the plumbing leak inside the house and create access for repair.