While visiting Houston, Texas, Mike and Kate tour the Johnson Space Center with an astronaut in the morning and at the Houston Astros' ball game that evening, the cousins search for the person who steals the astronaut's moonrock when he arrives at the stadium to sign autographs.

Cousins Mike and Kate investigate after someone threatens to tamper with the scoreboard right before the Colorado Rockies' season opener.

"While they are kayaking outside the San Francisco Giants' ballpark, Mike and Kate rescue an old ballplayer who has fallen overboard and discover his World Series ring is missing"--

When Mike and Kate visit Detroit, someone is blackmailing the Detroit Tigers' famous slugger, Tony Maloney. They've stolen his favorite trophy, and unless he fills the belly of a stuffed animal with signed baseballs, he'll never see the trophy again. Can all-star sleuths Mike and Kate track down the thief and save Tony's treasure?

Cousins Kate and Mike visit Kate's father, a baseball scout for the Dodgers, in Los Angeles just as a series of suspicious events lead him to think that someone is trying to steal his scouting reports.

"Babe Ruth's baseball glove goes missing before a Baltimore Orioles game. It's up to cousins Mike and Kate to find its whereabouts"--

"The president's brother is a catcher on the Nationals baseball team, and someone is stealing his equipment! Can Mike and Kate help the commander in chief catch a criminal?"--

During a visit to the Chicago Cubs' Wrigley field, cousins Mike and Kate investigate why someone has been tampering with the famous ivy vines growing on the outfield walls. Includes historical note.