In the ARC version the chapters read out THETOWERWANTSJOHNGAIUS
Alsoooo Judith mentioned the tower in her bout of madness, nona said she was afraid of it.
Also if harrow is headed towards a tower and gideon and ianthe are both tower princes??? WHAT DOES IT MEAN
The consensus so far is that the tower is canaan house, which probably has some unfinished business with John. Like in gtn when harrow suggested a secret room and Abigail said the same thing in htn.