Season 3, Episode 8- A Friend Indeed

Hugh has accidentally killed his wife Janice so calls his friend Mark for help. Mark goes to their house and makes it look like a robbery, whilst Hugh goes to a bar and makes an ostentatious phone call.
Mark is a deputy police commissioner and his wife is a rich shrew.
Columbo’s back appears at 15 minutes and 24 seconds, closely followed by the rest of him. He’s looking for his cigar.
Mark goes on to murder his own wife, drowning her in the bath. Later he gets Hugh to chuck her in the pool whilst he watches from a helicopter. Now it looks like a serial killing burglar is on the loose.
Columbo knows Mark did it as there’s soap in his wife’s lungs. Mark has the audacity to threaten Columbo, even telling him “you just lost your badge my friend”.
The columboid: Columbo sets up a real burglar to blackmail Mark, then plants a fake address in the burglar’s file, making sure Mark sees it. Mark then goes to the apartment to plant evidence but it’s Columbo’s flat and Columbo is there!
It appears we learn nothing about Columbo during this episode.
What did I do during this episode? Suggestions below please.