TV (?) movie about a blind detective.

I thought that this was a teleplay based on the blind detective Max Carrados, created by Ernest Bramah, but some research on IMDB rendered this unlikely. I thought the actor playing the 'tec was Robert Middleton, but nothing in his filmography seemed to fit.

I do remember parts of the story quite clearly. A series of apparent suicides, of people falling from a height, makes the 'tec suspicious. He uses himself as bait to trap the suspected murderer, who has actually been knocking people unconscious, then draping them over a high railing with their feet in the void, so that when they wake up and begin to struggle, they fall to their deaths. Diabolical, eh? So he figures out the modus operandi, then walks about in the danger zone, muttering to himself, "Be prepared for a blow to the head!" over and over. Sure enough, the murderer pops him and arranges him over the railing; but he is self-possessed enough not to struggle when he regains consciousness, saving his own life and catching the killer.

Definitely not LONGSTREET, BTW. The actor was middle-aged and slightly overweight. Anyone remember this?