HUMAN VS INHUMAN
To the reptilian mind - especially the intelligent type of planets like Sergan and Obrac - the lives of others were as nothing to the need for status.
To the feline mind - especially to the clever advisor of the master of Sergan - the agonies of others were not only of no consequence, they could even be a source of joy.
So when these two types of inhuman intelligences got together to defy the Terran orders against interplanetary kidnapping, space hijacking, and human slavery, it was definitely a case for a top-notch secret agent. Because Earth could not afford a showdown with more than one alien species at a time.
The secret agent was Cap Kennedy, Free Acting Terran Envoy, and his pursuit of the SLAVE SHIP FROM SERGAN turned out to be one of his most dangerous single-handed adventures.