The woman Dan Duryea has been following goes into a bar. He's seen from the inside spreading the horizontal bands of a venetian blind to see what's gong on but the blind would be on the inside of the window and he's supposed to be on the outside.
Duryea gets into the back of a taxi which Owens is already in. The taxi drives off, and the rear of the taxi is empty.
Owens uses the same taxi (as seen by its registration plate) on two consecutive days. Hugely unlikely with hailed taxis.