Against the Marquis of Mantua Gian Galeazzo devised a still more diabolical plot.

By forged letters and subtly contrived incidents he caused Francesco da Gonzaga to suspect his wife of infidelity with his secretary.[5] In a fit of jealous fury Francesco ordered the execution of his wife, the mother of several of his children, together with the secretary.

Then he discovered the Visconti's treason.

But it was too late for anything but impotent hatred.

The infernal device had been successful; the Marquis of Mantua was no less discredited than the Marquis of Ferrara by his crime.