Jonathan Creek (1997)

Daemons' Roost - S5-E4

Plot hole: The entire plot hinges on Jonathan's solution of the murder of the first wife of Stephen Belkin. That work had the effect of exonerating Belkin. But, Jonathan's solution wouldn't exonerate Belkin in the slightest. It only explained how the murder was accomplished. It did not eliminate Belkin as a suspect. Even after Creek's solution, Belkin still had means, motive and opportunity. As the only surviving person in the locked room where the murder happened, Belkin would have remained the most obvious suspect. In fact, Creek's solution tended to show that only Belkin could have done it, precisely because the room was indeed locked - Creek never explained how a third person could have got in and set up the killing. but in the transmitted episode, it only occurs to Creek much later that, duh, of course Belkin did it.

Senex