On 19 May 1517 Cardinal Sauli and Cardinal Petrucci were arrested in the papal antechamber of the palazzo apostolico and taken to separate cells in the Castel Sant'Angelo. They were placed in custody ‘it was said because they had planned to poison the pope’.

How did Sauli, a young cardinal, petted by Leo and showered with bene- fices, find himself in prison and in danger of his life? Had he, as some believed and still believe, been set up, or had he really thought that he, Cardinal Riario, Cardinal Soderini, Cardinal Castellesi and others still unidentified could stand by and watch the murder of a pope on Petrucci's orders via a third party and see him replaced by their candidate? Or was he the victim of his own lack of common sense: had he listened to Petrucci's ramblings about revenge for the loss of Siena and perhaps, for his own reasons, half-heartedly lent his support, but without taking him seriously?

How the plot was uncovered

Evidence of a plot emerged in April 1517 during the interrogation of the famigliari of Cardinal Petrucci regarding the cardinal's political crimes. The background is complex. In 1512 the French had been defeated, the Papal States consolidated (and indeed extended) and relations with the Holy Roman Emperor and Spain were, on the whole, on a sound footing. Leo, on his election, initially attempted to remain neutral when faced with the various proposed alliances between the main powers, which aimed to foster their own ambitions and further limit the claims of France on Milan but then, as was his nature, vacillated between one power and another.