The Motor Boys Across The Plains
is the fourth in the Motor Boys series. It continues the teens' adventures from both the second volume, where they became part owners in a Western gold mine, and the third volume, where they discovered a lost city and its riches. In the present novel, the teens are still in Mexico, heading back to the U.S. with Professor Snodgrass whom they added to their little band in the second volume. They barely get across the Rio Grande into Texas before they learn there's title problems with their gold mine in Arizona. Turns out that's just the start of their problems; adventures abound!