In the first episode of the HBO mini-series “Catherine the Great,” the empress of Russia is hunched over her desk writing about her political ambitions while her jealous lover stares into a hand mirror, primping for a cross-dressing masquerade at the palace.

“It just feels like something has changed between us,” he says, wearing a golden scoop-neck gown, his makeup half-done. Catherine (Helen Mirren) wears a man’s suit with a tricorn hat that makes her look like an American revolutionary.

She rises from her desk, strides over to her male companion and, in a few succinct sentences, puts an end to their yearslong romance.

“You want something I cannot give you,” Mirren says simply. “You want power.”

Her lover, Count Orlov, who helped engineer the coup that unseated her husband, Peter III, thinks it is time to marry her and take on a more powerful role in her regime. But Catherine sees an army of men encircling her, plotting ways to co-opt her authority, and she has no intention of giving it up.