The bait
Internally, Dan questioned ; ' did you really not know I was here ? Do you really believe me to be that much of a fool ? '
First of all, this is Harvest mansion.
Sure, they kept Olivia under house arrest, not the rest of the Harvests.
William Harvest was the lord of this castle.
In any castle, lord's study was the most important place. Even if Harvests left it empty for themselves to use, leave such a place unsupervised ? ' impossible. '
It's impossible even for the most stupid and airheaded lord.
Someone would definitely monitor the room, for good or bad.
Lady Olivia has such a good spy network, she gets the information about what queen ate for morning breakfast by the dinner in Sasha's words. For god's sake, they assassinated the king right under Tyrant Lustre's eyes.