 In summer 1605 Garnet met with Robert Catesby , a religious zealot who , unknown to him , planned to kill the Protestant King James I. The existence of Catesby 's Gunpowder Plot was revealed to him by Father Oswald Tesimond on 24 July 1605 , but as the information was received under the seal of the confessional , he felt that Canon law prevented him from speaking out . Instead , without telling anyone of what Catesby planned , he wrote to his superiors in Rome , urging them to warn English Catholics against the use of force . 
