For a while the Almeida Theatre seems too small to contain her energy. Earlier this year, her extravagant gestures filled the Queen Elizabeth Hall to perfection, but here, at least at first, it feels as if she's over-acting - though perhaps it's the alarming proximity of those flashing Garboesque eyes. By the second half, which she devotes to Kurt Weill, either she is used to the space or we are used to her, for the Almeida seems purpose-built.
She sings in a sensual mixture of German and English, reserving her mother tongue for the most guttural passages, bouncing her ferociously rolled "r"s off the Almeida's walls. In "Sex Appeal" she stretches out the line "Oh God" for a knee-weakening eternity, her voice descending the scale until it is a Geiger-counter croak of unslaked desire. A collective tremor of pleasure oscillates round the theatre.
It is sexual ambiguity that fires her most. In "Gesetzt den Fall" ["Oh Just Suppose"], a song about gay lovers, she is a predator on the prowl. When Vanessa in the second row was leaving for the theatre that night, she probably didn't expect to end up dancing cheek to cheek with a siren like Lemper, but she finds herself being led on to the stage. "Put your arms around me," Lemper tells her, and they twirl tenderly. "You're going to have to leave your husband," she says. "Send him home after the show and come to my dressing room."
Later, she turns Brecht and Weill's "Moon of Alabama" into the evening's centrepiece. "Oh show me the way to the next pretty boy," she sings, then murmurs, "I must have a pretty boy," taking a hapless chap by the hand. "Come on, pretty boy - on your knees," she says. Then she clasps his head to her bosom: "Let me be your mummy."
If it's not sex it's money. "Marx said everything belongs to the state - the state of Almeida, or the state of Lemper for tonight," she says when she comes to the lines in "Alabama" about the pursuit of the almighty dollar. Lemper frisks one man, relieves him of his wallet, puts his credit card down one cup of her bra, and shares out the rest of the contents. Another punter is accosted, and she stuffs pounds 20 down the other cup, redistributing the rest of his cash round the front row. "In the state of Almeida, anything is possible," she declares.
"These have all got mixed up," she says at the end of the show as she rustles in her bra. "It's hot down here - the magnetic strips probably won't work." And off she goes, leaving the booty on the piano for the victims to sort out. Willing victims they were too. We were all willing victims.
Almeida, N1 (0171 359 4404), until 24 Jun.Reuse content