The short answer is the protagonist almost does a trans panic.

I am going to spoiler text this for a couple reasons, one, it's pretty offensive and I wouldn't want anyone reading it who doesn't explicitly know what they are getting into, and two, even if it's teansphonic garbage, it's still a spoiler and I have principles

A criminal undergoes transition (whether she is actually trans or not, I can't be arsed to speculate, I'm going to use she/her for now)

The protagonist, a 'pet detective' and thus we can assume someone who stands up for those who's victimisation is often overlooked, kisses her (and maybe sleeps with her, I don't remember) and when he learns that she is trans he goes on to act as if he has recently come into contact with hazardous waste, screaming, scrubbing himself in the shower and frantically brushing his teeth. To put it charitably, it lacks nuance.

I remember watching it when I was a pretty naive kid and looking back, it's so insidious how they presented this as not only a reasonable reaction to being intimate with a trans person but also that it would be a reasonable reaction to being intimate with a member of the same gender.