“Give me back my beast.”

That was Greta Garbo’s famous (perhaps apocryphal) plea after she saw Jean Cocteau’s “Beauty and the Beast.” It echoed in my head as I watched the new season of “Killing Eve”: Give us back our beast. Give us back our Villanelle.

It was remarkable when the second season of “Killing Eve,” the dark and delightful comedy about a spy, an assassin and their mutual obsession, was as good as the first. Phoebe Waller-Bridge, the original showrunner and head writer, had turned over those duties to Emerald Fennell, and the writers of Season 2’s eight episodes were entirely new. But the electric, erotic, sardonic architecture remained intact; the souffle didn’t collapse.

For Season 3, which premieres Sunday on BBC America and AMC, the show has changed up its staff again, replacing Fennell with Suzanne Heathcote, a writer on AMC’s “Fear the Walking Dead,” and using all new writers and directors (through the five episodes available for review). And this time the news isn’t so good.

“Killing Eve” isn’t a bad show now, but it’s a different show, in depressing ways — less vital, more ordinary. It is still shocking here and there but largely devoid of surprise. A mordant and sexy comic thriller edged with terror has become a competent psychodrama bordered with sentimentality. The air has gone out of it.