A ghost is supposedly haunting a mansion in Transylvania, and the girls must figure out who or what is actually behind it. The "ghost" ends up being the caretaker of the mansion who is also a beekeeper. (The trip to Transylvania was about 9,000 miles from their attic) 2. The Case of the

Pungent smells and weird noises plague the "Logical I Ranch". Some employees of the ranch think it is being caused by a dragon running loose. (The trip to Dead Gulch USA was about 1,372 miles from their attic)

The girls' parents work at Sea World as over-worked dolphin trainers. One day, the girls run into a dead body in the woods that eventually leads them and their parents to a cruise ship while trying to solve the rigged mystery. The boss of the girls' parents had planted evidence to get them all on the cruise, so they could take a much-needed family vacation.

The sequel to The Case of the Sea World Adventure. Mary-Kate and Ashley's father has a laptop containing vital information. It gets stolen while on a cruise ship and must be retrieved. The twins believe a friend of their father's was responsible, but it later turned out to be a staged occurrence.

Something is making scary noises inside the fun house at an amusement park, and the girls must figure out who or what it is. Using the clue of "Monster Mush" and "bananas", they find out the monster lurking inside the fun house is really an orangutan. (The trip to Tons-Of-Fun was about 1,379 miles from their attic)

Hackers break into Santa's computer to steal the "Spirit of Christmas", the plane Santa uses to fly to deliver all the presents to the children of the world on Christmas Eve. It is up to girls to show what the holiday is all about. (The trip to North Pole Drive was about 1,000 miles from their attic)

A space shuttle has been grounded, due to a mysterious tapping sound coming from its outer surface. Unless the girls can figure out what is going on, the space shuttle will be not be able to lift-off. To figure out the mystery, they get help learning about space travel through the U.S. Space Camp program. (The trip to Huntsville was about 1,643 miles from their attic)

Three pirates claim that the sharks at a Sea World exhibit are singing, and the girls must figure out where the strange sounds are coming from. (The trip to Orlando was about 2,500 miles from their attic)

The girls travel to Hawaii, where they meet a hotel manager who has been dealing with a string of recent disappearances around the hotel. (The trip to Hawaii was about 2,556 miles from their attic)

The girls receive a call from some miners of marshmallows that a snowball-throwing monster has been "terrorizing" them. The girls eventually find out that the "snow" is really ash, and the "monster" is actually a geologist warning them that an active volcano is not a safe place to work. (The trip to Jelly Island was about 1,759 miles from their attic)

Unidentified flying objects have been seen flying overhead. In this case, the girls get help from the United States Navy to solve the mystery. The "UFOs" ended up being a satellite that was flying too low in orbit. (The trip to The Edge of the World was about 3,528 miles from their attic)