On a trip to the dentist's office, Ben grows uneasy over the dentist's odd behavior and goes into hiding, but when his suspicions prove right, and the dentist transforms into the monstrous Toothache, Ben must save the day!.

Team Tennyson participates in the inaugural ride of the Sonitrain, the fastest train in the world, but when the conductor turns out to be Lord Decibel, Ben must derail his master plan if he is to save everyone on board the runaway train.