Bon Voyage, Charlie Brown (and Don't Come Back!) (1980)

Charlie Brown, Linus, Peppermint Patty and Marcie travel to France as foreign exchange students. Also along is Snoopy and Woodstock. While everyone is excited about the opportunity to travel to a foreign country, Charlie is disturbed by a letter he receives from a mysterious girl from France who invites him as a her guest only to find that he does not seem welcomed to her Chateau.