This was the first televised episode of the Columbo series (although it was filmed after "Death Lends a Hand")and it heralded one of the most successful TV series in history.
Jack Cassidy (who played the murderer in the series three times) enthuses smugness, arrogance and self-assuredness in equal measure here, as Ken Franklin, one half of a mystery writing team who hatches an elaborate plot to kill off his partner, Jim Ferris (played by Martin Milner) who decides to terminate their professional relationship, leaving Franklin exposed as merely a good publicist rather than a prolific writer.
The initial murder set-up is fantastic and Cassidy's performance facilitates an arguable accolade that he was the best Columbo murderer in the series.
Peter Falk is wonderfully understated in his role as Columbo and the character's inherent traits and oddities, which are underlined by a seeming slowness and absent-mindedness, contrast particularly well with Cassidy's character's extreme smugness: one of their early scenes together where Ken Franklin fabricates a motive for the killing through Jim Ferris's non-existent expo-see of identifying hit-men operating in the underworld exemplifies this very well. Franklin hints to Columbo this potential motive and Columbo (purposely or ignorantly) fails to latch on, forcing Franklin to express his disappointment in a markedly patronising manner and compare him unfavourably with the detective in the books, Mrs. Melville.
Also, noteworthy is the early directorial contribution of 24 year old Steven Spielberg. Notwithstanding, some elementary inclusions of cameras shadowing the actors and actresses, he adds some stylish and elaborate touches to uphold the general professionalism of the episode. One particularly stark image is of Jim Feriss's dead body lying on the settee, almost dark in the foreground, as Ken Franklin raises a glass to him in the background after he finishes answering a phone call to Ferris's distraught wife. I have no doubt that working to a restrictive 10-14 day schedule, Spieberg's efforts should not be underestimated.
Unfortunately, the event of the second murder, necessitated by a blackmailing scheme which is plotted by a female friend of Franklin's (and ironically referred to as "sloppy" by Columbo in his climatic summing up) takes the steam out of the whole thing. The cutting edge of the plot is compromised and the screen-time between Falk and Cassidy inexcusably lessens at this point to perhaps help the script-writer (Stephen Bocho) out of a tight corner, since he cannot singularly develop the story without another murder.
The climax is the most disappointing aspect of this episode. The initial banter and exchange of words between Falk and Cassidy is strongly and effectively executed, but it merely advertises the fact that it should have happened more in the episode. The main aggravation lies with the sealing clue (if it can be called a clue): Cassidy's character's hitherto smugness and arrogance is amazingly expelled by a clue that really does little to imply his guilt; and once this is mentioned, he capitulates in a rather unspectacular and uncharacteristic fashion.
All in all, a bold opening to the series, which inevitably advertises and foretells all that is good about Columbo, and, conversely, the problems associated with such ingenuity, i.e maintaining the high standards and particularly, creating a credible and suitably intelligent ending.

Loved Part One, The Impossible Planet, but whoops, what a disappointment part two 'The Satan Pit' is. The cliffhanger of something apparently rising out of the pit was - nothing coming out of the pit. Then ages spent crawling round air vents to pad out the story, the Beast a roaring thing empty of intelligence, so no Doctor/villain confrontation I'd been anticipating. The TARDIS is somehow inside the pit despite the pit not being open till long after the TARDIS fell through the planet crust. And finally another ready made solution which existed for no logical reason - I mean, why not plunge the Beast into the Hole as soon as the pit opened? Why not plunge him in all those years ago instead of imprisoning him anyway. Why not - I could go on but I've lost interest...