My hero, who is pronouncing his name as Gee-yohm, is blinked into existence in Mary's home in England in 2018. His dress and appearance (T-tunic and leggings) are well-worn medieval European. He doesn't speak a language that Mary recognizes, and her attempts at English, French (which she knows a little), German, and Italian come up with just shakes of his head. Mary deduces that the hero's name is the French Guillaume, and that he has time-travelled into her home, perhaps from Norman England.
She doesn't want to turn him over to the authorities. She decides to keep him and teach him English, but she doesn't know how to get him documents that he will need to exist in modern England. She worries that he is bound to get sick from modern germs, and will need to go the doctor. How can she go about "legalizing" him? Posit that she doesn't know how to obtain those documents via illegal channels.