London’s ancient magical secret societies have been reawakening, and no one is quite sure why. Since her adventures with George and the newly reinstated Claw and Spark Alliance, Attie and the junior Ink members have helped several new groups discover secrets that were supposed to have been forgotten. Their success with the London Ghost Coalition (a group that can talk to the ghosts of anyone buried in London) led them to help revive the Wish Workers Association (who can use wishes from all the coins tossed in London’s fountains). They, in turn, recommended Attie to the Urban Animal Squad, whose spy network reaches all across London. 

Attie can’t resist one last group in need, and when she and the junior Ink members are visited by the last remaining member of the Silt and Treasure Guild — Caspian Atwater, who has the power to speak to the Thames, she comes his aid. Caspian can throw magical messages in bottles into the river, and the river answers back using the objects that it washes ashore. But lately the River is sending messages that don’t make any sense, and they’re getting more urgent and chilling - the River is littering the foreshore with ancient bones.

The team get to work on the case, but it turns out that the Emerald Ink Society has been keeping its own secrets for the past several centuries. And by helping the new secret societies harness their magic, Attie is playing right into the hands of an old enemy. Packed with ghost magic, wishes, animal spies, dragon statues come to life, and of course magical green Ink that can move mountains, this is the third and final instalment in the Attie and the Worldbreakers series.