Ippolito wanted him for his chapel[3][4] and, near the end of 1504, coming to Ferrara during the illness of their father, abducted Rainaldo and held him in the Fortress of Gesso (which belonged to Giovanni Boiardo, count of Scadiano).
In May 1505 Giulio discovered where Rainaldo was held and, together with Ferrante and other armed men, recovered him, and, in a sign of defiance towards, replaced him in his cell with the warden of the fortress.
On 3 November 1505, while Giulio was returning from a trip to Belriguardo, he was surrounded by servants of Ippolito, who had ordered them to kill his half brother and tear out his eyes.
[3][4] During one of the frequent absences of the Duke,[3] the spies of Ippolito gathered evidence about the plot, but before they reached Alfonso, both Lucrezia and Isabella advised Giulio to flee to Mantua where he would be protected by Francesco Gonzaga.
[citation needed] While the other conspirators were executed, the sentences of Giulio and Ferrante were reduced: they were imprisoned in the Leoni Tower with Castello Estense, and their property was confiscated.
He supposedly caused a commotion among bystanders when he returned to the street because he retained his charm and an erect posture, and dressed in the fashion of 50 years before.