Having made a huge sum from his deal with the oil company, Jack is mixing in London high society. He is sought by his land agent Frank to help broker the sale of an expensive emerald necklace to Morty, Jack's old American colleague, on behalf of wealthy Philip Martin, with a commission for them both. Martin's sister Jane takes a shine to Jack but proves to be unhinged and willing to kill for the necklace. The sale goes ahead and when Jack learns that Morty paid off the mobsters who were threatening him, he waives his half.