Allie is looking forward to her class field trip - even if it's only to a historic one-room schoolhouse. Riding on a bus is something Allie usually misses out on, living so close to school, and some of her friends are dressing-up in old-timey costumes. But then Mrs. Hunter announces that every student in Room 209 has been assigned a 'buddy' for the day-from Allie's old fourth grade class at Pine Heights Elementary-and her buddy just happens to be her ex-best friend Mary Kay, who betrayed Allie right before she moved! And, as if things aren't bad enough, with renovations going on at Allie's house-there's a hole in the wall that her kitten, Mewsie, keeps disappearing into. What if Mewsie gets trapped inside the wall forever? With her past catching up with her, it looks like this is one trip Allie's going to need to write some major rules for.