Jeromy and Jason face hard decisions regarding the "KBG," whether or not to get into a car, and how to properly get to shore. They also get a Mark 3K harpoon gun and have a whale of a time using it!

Jill and Jeromy face hard decisions regarding their hunger levels, Melissa the cat, and storage rooms. Also, none of the endings make sense, soooo… that’s something to look forward to?

Jason and Jill face hard decisions regarding planetary citizenship, black holes (AKA space caves), and laser radios, and never do figure out what that metal thing their mother gave them was.  Also, Mermah's coming along whether they like it or not.

Jeromy and Jason face hard decisions regarding possible 1980s casual racism, stalactites, and a dog named Harry, all after ditching the titular balloon almost immediately.  This book also instructs them to resolve a life-or-death decision with a coin flip... and they do!

Jill and Jeromy face hard decisions regarding ledges, grottos, and hatches of unknown metal, all in a quest to find the lost city of Atlantis. Also, something about a human zoo.

Jason and Jill face hard decisions regarding wooly mammoths, mad kings, and the Loch Ness monster... and never do make it into the future. Wut wit dat, yo?!