He traveled barefoot to Italy in sackcloth at the time of the Black Death. Once there, he helped and healed until finally he caught the plague himself.
He crawled off into the woods to die alone so he would not infect anyone. He was saved by a mysterious dog, which came and fed him until he was well enough to limp homewards.
Here he was arrested as a spy because no one could recognize or remember him. So he died in prison.
The only good news we can supply is that as a Saint he has been united with the dog.