Mark and April are sent to Denmark to rescue Stanley Umlaut who has been kidnapped by Thrush. Stanley, unknowingly, has eaten a piece of Danish blue cheese that contains a microdot hidden by Thrush agents.

The King of Drublegratz is dying. The heirs to the throne are his three sons, but THRUSH wants to take over the country. They send Dr. Igor Gork with his sound projector. As one of the sons drives across a bridge, Dr. Gork uses the projector to destroy it. April and Mark are sent to prevent any further deaths in the Royal Family.

A French School for Civil Administrators always plans a commando exercise for its graduating students. Waverly knows that there is some kind of hijack being planned so he sends April and Mark to investigate.