Luke Mountfathom knows he is special and odd. He is told so by everyone he knows. His parents are special and odd too - they are the keepers of the House of Mountfathom, a magnificent stately home where the wrong door could take you to a far away land, and strange animals appear to stalk the grounds at midnight. The house is his home - but it is also the headquarters of the Driochta, a magic-weaving group of poets, artists, politicians and activists charged with keeping the peace in Ireland. They have many powers - have mastered Mirror-Predicting and SmokeSummoning and Storm-Breaching - and a final ability: that of Mogrifying; taking on a unique animal form.
But Luke's idyllic existence at Mountfathom cannot last. Word reaches the House of protests across Ireland. There is a wish for independence, a rising discontent and scenes of violence that even the Driochta cannot control. In Dublin, death and disease is running rife in the tenements; a darkness is clogging the air, and is intent on staying. And when things quickly spin out of control for the Driochta, it is up to Luke, his cat Morrigan and his best friend Killian to worm out the heart of the evil in their land.