It has to be said evenings aren't Isobel's favourite time.
She enjoys her bath, that much is true. But, otherwise, she could very well shout the whole evening through.
Unfortunately for PD this the only time he gets to see his darling daughter - not ideal for bonding.
I think the witching hour is actually 5-6 though: whatever Isobel does then sets the tone - if she doesn't take a nap it is unlikely that she will until ten.