Most who know Sam Spade as a character played by Bogart will find this peculiar, but the explanation is right there in the box: “Listen to ‘The Adventures of Sam Spade’  every Sunday. It was a wildly popular show for a few years, sponsored by Wildroot hair-goop.

Apparently a guy’s having mechanical problems with his flying machines, so naturally he calls in a private detective.

The blonde is Effie, his adoring secretary:

It's dog-eat-dog in the skywriting trade.

Eventually Wildroot stopped sponsoring Spade over Hammett's Redness - but not until the partnership yielded these ads.