Titus Oates convinced the Whigs in Parliament that he knew who was in on this plot and he was given the authority to round up the suspects. At the trials for his accused, any witnesses they brought forward would be discounted by the Prosecution and the Judge, because, of course, they were also Catholics and if not in on the plot were probably in favor of the plot! After one of these manifestly unfair trials, five Jesuits were martyred on June 20, 1679 at Tyburn Tree in London:
The circumstances of their execution were quite dramatic. All five were standing in a cart under the scaffold, with their hands bound and the nooses around their necks. They had each spoken, each prepared themselves for death, when suddenly, a rider galloped up, crying "A Pardon, A Pardon!"
Charles II issued them a conditional pardon to spare their lives--all they had to was admit their guilt and tell him all they knew about the plot. Trouble was that they weren't guilty of any plot and they couldn't tell him what they knew because there wasn't any plot in the first place! They declined the pardon, protesting that they could not lie to save their lives--they could not risk their immortal souls to save their physical bodies.
Therefore, they prepared themselves again for death--the rider returned to Charles II with the news--the cart pulled away and they were hung until dead before their bodies were quartered and their heads cut off.