Magic Tree House Merlin Missions Dogs in the Dead of Night (Used Book) - Mary Pope Osborne
Beware of avalanches! When the magic tree house whisks Jack and Annie back in time to the highest pass in the Swiss Alps, they discover an ancient monastery filled with monks and Saint Bernard dogs. Annie can’t resist offering to train a wild young dog named Barry, but he is quite the handful! Before the night is over, Jack and Annie will be forced to use some crazy magic!
Magic Tree House # 18