In 1815, while making his living through fur trapping and some cod fishing, he discovered that one of his fishing boats had been cut adrift and its sail and fishing tackle had been stolen, presumably by Beothuk Indians who lived in the area.
Two years later, several of his traps used to catch marten were also stolen. The following year John Peyton was dismayed again to find that a boat he had loaded with salmon was also cut loose and its cargo stolen. At this point, he decided to put an end to this thievery and organize a small party of men to help him get his property back. He also hoped to gain the cooperation of the Indians in order to prevent any further damage to his property.
After several days travel up the Exploits River, they captured an Indian woman called Demasduwit, who the locals named Mary March because she was captured in the month of March.
John Peyton took the captive woman to St. John's, with the intention of eventually returning her to her people laden with gifts as a token of friendship. Unfortunately, Mary March died of tuberculosis on June 6, 1829. She was believed to have been the Last of the Beothuks.