On Your Guard! (Annual story)

On Your Guard is a 1988 annual story.

Plot
Bill and Ben have been warned to be on their guard, but don't understand what it means. Ben hears some noises overnight and sees a dark shadow. It turns out to be some thieves. They are shocked when they think they are seeing the same engine over and over again and make a run for it instead. Bill and Ben tell their drivers about it the next day, and say they think the thieves were trying to play hide and seek with them. Their crew are sceptical about the claims.

Characters

 * Bill and Ben
 * BoCo (mentioned)