At first, horror film actor Boris Karloff seems a strange choice to play Joseph Conrad's infamous "Mister Kurtz".
The part has generally falls to serious method practioners, notably John Malkovich and of course Marlon Brando by way of Apocalypse Now.
In another sense though, he is a perfect choice, his accent suggests debauched plumminess, and as a noted horror player he gets the sheer strangeness of the setting.
We ought to think of Karloff, like John Barrymore or Charles Laughton as a sort of artistic bridge from the English Classical Acting Tradition over to the Internal Rigors of the Method.
This is a process accelerated by the particular needs of sound film acting wherein voice is added to movement and there mere tone inflection and ferocity can divert, stop or speed up the action.
The method could never prosper in silent cinema...once films began to talk and once TV came in the need for intensity and intimacy became paramount.
Karloff isn't a method player but he is sufficiently intimate with his own emotions to deploy them to advantage in an intimacy-driven acting enviroment like a live television production.
Tonight's show is a happy artistic accident.
Boris Karloff had bought himself out of his contract at Universal in 1940 because he was unhappy with the shoddiness of the writing for his signature horror parts. He puttered around Hollywood for several years as a independent and then counterintuitively made his way to New York where he had several successes on Broadway (notably as Captain Hook in Peter Pan) and was readily availble for guest appearances on radio.
When TV came in, he was one of the few famous Hollywood actors unencumbered by a Studio Contract which would've otherwise restricted his ability to appear in that upstart medium.
Which is why all through out the 1950's Karloff turns up in things like Schlitz Playhouse, Lux Video Theater and tonight's Playhouse 90 Production of the "Heart of Darkness". He also hosted several anthology TV shows and appeared on shows like "Route 66".
TV was the re-making of Boris Karloff, his films where all sold to television in the mid 1950's so his old parts were suddenly widely distributed. His TV work demonstrated that his current acting skills were as sharp as ever, soon enough the phone was ringing again and the Prodigal Monster returned to Tinseltown bidding on something akin to his 3rd Comeback.