The wealthy jeweller to the nobility plots to betray the crown to Spain.

Matthew Stock’s young relation, Thomas, leaves home to apprentice himself to Castell, a jeweller in London. Then he disappears. Castell writes to say Thomas has gone to sea, but Stock decides he must investigate as such a move is unlike the boy.

While Stock is away, Thomas returns and tells Matthew’s wife Joan how the jeweller is trying to have him killed. He has discovered that Castell is blackmailing high-ranking members of Elizabeth’s court. Joan must rush to London to warn her husband. For Matthew has no idea of the danger he is in, asking the ruthless Castell about Thomas…