Derrick is just a sexually frustrated husband who wants to put a little spice back into his marriage. Feeling unloved and unappreciated, he just wants to see his cold, disinterested wife return to the adventurous woman she was when they first started dating. She, of course, waits in the car while he pretends to be buying a dildo for a friend's bachelor party.
Had Derrick not been so curious, and had his wife not been so cold, things might have turned out the way he intended. Instead, he decides to try just One Little Sip of the potion Magda provided, half-certain that it's just a liquid form of Ecstasy. What begins as a suspect case of the flu soon takes on frightening implications has his body begins transforming, fueled by what his doctor dismisses as a stress-induced estrogen imbalance.
Where it begins to get weird is when Denise, his wife, starts slipping up, misgendering him, and misremembering details of his life, confusing him with a daughter they never had. Where it gets weirder is when Derrick starts having memories of highschool boyfriends he, clearly, never had as a boy.
Rather than spoil the magic, I'll stop there and let you imagine for yourself just what is happening to poor Derrick and why. It's actually a lovely little tale, well thought out, and well orchestrated. Bloom always does a wonderful job of exploring the consequences of her transformations, and that talent goes even deeper here.