First Great Western said Polly the cat is believed to have stowed away in a sealed unit under the high speed train's front carriage after breaking her leg near her Plymouth, England, home Jan. 10. The cat was not discovered until the end of the next day, after trips to London, Swansea, Worcester, Oxford and Paddington, The Mirror reported Thursday.
Train manager Emily Mahoney-Smith found the cat after hearing the cat whine during a stop.
Veterinarian Matthew Berriman of Penzance, England, said Polly's leg had to be amputated.
"She had a very nasty leg fracture which was easily four or five days old by the time we operated," Berriman said. "So it's extremely possible she was stuck on the train for several days."
Polly had an identification microchip and has been returned to owners Arthur Westington, 84, and his wife Louisa, 82, who said she is recovering.
"We thought she'd gone for good. She has now seen more of the country than us," Louisa said.