A Triolet. Spoilers(ish) for Winter Holiday and Secret Water? Written for the "expedition" challenge at fan_flashworks.
A map hangs on the playroom wall,
And an old plague flag, side by side.
Keeping the Walkers' eyes in thrall
A map hangs on the playroom wall.
Two expeditions to recall,
Swallows and Amazons allied -
A map hangs on the playroom wall,
And an old plague flag, side by side.
(Note: technically the Swallows had quarantine flags, and only Nancy had the actual plague flag - but I'm calling it artistic licence ;) )