(possÃble spoilers)
Russian Grand duke (Robert Young), disguised as Romeo falls in love with his Julia (Maureen O'Sullivan) during a masked ball. She had been assigned to him by her government to save the life of her father, a polish freedom-fighter. A secret agent (William Powell) is enlisted to deliver a secret treaty, hidden in a candlestick. Meanwhile the russian secret police sends a female spy (Louise Rainer) after him. Mission: replace the treaty by a death warrant for Powell - equally hidden in a candlestick. It goes without saying that a) Powell & Rainer have already crossed their swords, and b) the candlesticks are exchanged by mistake more than once...
The story in itself does not give you automatically an idea of the film's qualities. Witty screenwriters, skillful directors, talented stars have made delightful films out of even slighter plots. But not this time. Powell delivers his lines with eye-twinkling charm but he is no match for his leading lady: You know how all actresses, without exception act during the ball/party scene, when they flirt with their leading men while they are slightly tipsy? This is how Rainer acts - throughout the film. It is embarrassing to watch. A very poor film.