Complex sentence: McKay becomes convinced that there's a rat and eventually starts to suspect Paudge, the bureau is brought in to investigate but Paudge is given the all clear, but McKay isn't convinced.
Split into simpler sentences: McKay becomes convinced that there's a rat and eventually starts to suspect Paudge. The bureau is brought in to investigate, and Paudge is given the all clear, but McKay isn't convinced.