Tisquantum, commonly referred to as "Squanto," met the Plymouth colonists in March of 1621 as part of a three-person delegation of the Wampanoag people. Massasoit, the sachem of a nearby community, and Samoset, a sachem for a Wampanoag community to the north of Massasoit's, brought Tisquantum as a translator.

He had learned English because he had been captured (with 27 other members of his tribe, the Patuxet) by English sailors in 1614, initially being sold as a slave to the Spanish. He escaped Spanish captivity in circumstances that are somewhat unclear, and made his way to England, from where he was sent to Newfoundland as part of a settlement scheme. In Newfoundland, he met Thomas Dermer, an acquaintance of John Smith's and an explorer of what's now New England, and became an interpreter for a further voyage of exploration in New England. Returning with Dermer to his village, he found it abandoned, and after several brushes with hostile natives during which Tisquantum played a role as interpreter in calming the conflicts, Dermer left him at a native settlement in Sawahquatooke (modern Saco, Maine).

It's not clear how Tisquantum ended up living with the Wampanoag, and whether he was left at Sawahquatooke as a prisoner or a guest, or something in between. What does seem to be the case, though, is that his story was not unique -- English (and other nations') explorers regularly captured natives in the New World and brought them back to Europe as slaves or curiosities.