Knights of Bonalla. The Third book in the series Frogger

Knights of Bonalla. The Third book in the series Frogger. ok:
Knights of Bonalla is a series of books written around the adventures of Brad and Lee. Zoom One is the first in the series, followed by Commando. Frogger tells the story of one of the adventures that didnt go quite to plan. Brad and Lee discover an unwelcome stowaway clinging to Zoom One when they return to their base on Goanna Hill. The stowaway creates a problem they could never have imagined in their most awful dreams! Worse is to come, the secret they have guarded for so long is discovered! This just makes the situation the boys have got themselves into even more of a worry