Former jewel thief Michael Lanyard toys with a princess and a grand duke.

Once a jewel thief always a jewel thief? Yes and no. Yes if you consider the fact that Michael Lanyard also known as the Lone Wolf once retired from the "trade" but relapses back into his old habits when he is tempted by the emerald pendant of beautiful socialite Marcia Stewart. The trouble (?) is that he falls for the belle and he soon gets more interested in getting the girl than the jewels that adorn her. What he wants now is to return the pendant but a rival gang interfere and force him to take part in a big-time caper.