The Mystery in Old Quebec by Mary C. Jane, 1955.
Mark and Kerry, a brother and sister, are visiting Quebec with their father, who is on a business trip. Their father allows them to explore the city on their own during the day while he works (something that would be unlikely to happen in modern times). The kids enjoy sight-seeing and learning French words and phrases. They even make a new friend in the city, but they are troubled by events at the quaint little inn where they are staying.
On their first day there, Kerry’s coat mysteriously disappears and reappears with some strange messages in the pocket. A boy wants them to take a message to someone in the city. At night, Kerry hears someone crying in the next room. Is the boy being held prisoner at the inn? If so, why? Kerry and Mark are determined to help in any way they can, but time is running out.
The book is currently available online through Internet Archive.
My Reaction and Spoilers
The solution to the mystery involves family quarrels, custody issues, and racial tensions. In spite of that, this is actually a very gentle story. In the end, the kids are dependent on the people the mysterious message was intended for to help a troubled, lonely child. It turns out that the boy is an orphan, and some of his relatives are white, and some are First Nations (Native American). There is a fight for the boy’s custody, but the boy knows where he really wants to be.
The author describes the atmosphere of Quebec in some detail. The famous landmarks probably haven’t changed much, although I don’t know if all the descriptions are accurate anymore. I also thought it was interesting how the author includes some French phrases and their pronunciations and translations as the kids learn to communicate with French-speaking people in the city.
Terror on Cemetery Hill by Drew Stevenson, 1996.
Toying With Danger by Drew Stevenson, 1993.
It seems that Sarah is right that someone is trying to spy on Dr. Becker. The kids learn more about the money involved in buying and selling toy designs when they visit the Too Wonderful toy company for a tour with Sarah’s grandfather. Making toys is serious business, and companies guard their designs very carefully. The Too Wonderful toy company wants to purchase some of Dr. Becker’s designs, but one of the members of the company says some strange things about Dr. Becker. Can the kids trust him? Can they trust the strange Dr. Becker? Can Sarah catch the spy before it’s too late?
One Ghost Too Many by Drew Stevenson, 1991.
Sarah persuades Clark and his friend “Frog” Fenniman to join her investigation of the house, but besides the resident ghost, they will also have to deal with a local group interested in psychic phenomena and a mysterious stranger who is paying the local bully to spy on the house.
The Mystery on October Road by Alison Cragin Herzig and Jane Lawrence Mali, 1991.
The Talking Table Mystery by Georgess McHargue, 1977.

The Ghost on the Hill by Grace Maccarone, 1990.
When they reach the state park, Dennis Ten Foot Bridge, who is the last of his tribe, tells the students about his tribe, teaches them wilderness skills, and leads them in group activities. One evening, Joey goes out to practice some rowing on the lake by himself, and he sees what looks like a large ghost at the top of a hill However, everyone knows that Joey lies about a lot of things, so at first, no one believes him. At least, no one except Adam.
The Return of the Third-Grade Ghosthunters by Grace Maccarone, 1989.
They try to use scientific methods to study the haunting. They measure the placement of the furniture to see if anything moves while they’re out and sprinkle flour on the floor to get footprints. But, even though they watch carefully and don’t see anyone enter the bunk house, when they go inside, everything is a mess, and the flour doesn’t appear disturbed. Everyone else is about ready to admit that this one is a real ghost, but Adam has another theory.
The Haunting of Grade Three by Grace Maccarone, 1984.
Most of the group members are misfits in one way or another. Norma Hamburger is a shy girl, frequently teased about her last name. Debbie Clark is a talkative girl who’s really into science. Chuck Webber, Adam’s best friend, is the class clown, always telling stupid jokes (and one of the main people who teases Norma about her name). Danny Biddicker is strong and good at sports, but he worries that he’s not as smart as the others. Joey Baker feels overshadowed by his large family, so he tells tall tales to get attention. The other kids don’t understand and get annoyed with his lies. By working together, they not only learn the secret of Blackwell House, but they learn more about each other and become a real team and friends.