The Red Herrings in Great Northern are Peggy, Susan, Titty, Roger and Dorothea. They are sent out to distract the Gaels while Dick is photographing the Great Northern Diver on the nest (GN21). They go as walkers, and Roger escapes from the party to get his revenge on the young chieftain Ian for labelling him The Sleeping Beauty. On their previous trip up the valley, the party decided to be geologists and make a noise with stones, leading the McGintys to think that they have been sent to disturb the deer and chase hinds off their breeding grounds. So if they come back they are to be captured, to find out who put them up to it (GN16).
At the same time the Decoys, John and Nancy are sent out to distract Mr Jemmerling. John is disguised as Dick with imitation goggles or glasses made of black cork marks on his face. This works until the sailor gets too close a view of him (GN20)
But Dick the photographer, the Red Herrings (including Roger), the Decoys, and Captain Flint (who has seen the others being marched away) are all rounded up and imprisoned by the Gaels. But they persuade The McGinty that Mr Jemmerling is their mutual enemy when they all hear the shot he fires at the Great Northern (GN26).