"Miss Kaye lingered over pudding, evidently with the intention of allowing the latecomers a few extra minutes, then, rising and saying grace, she announced:
'Linda Marshall and Sylvia Lindsay will come to my study at a quarter to two,' and left the room.
'We're in for it now,' said Linda, clasping Sylvia by the hand as they met in the passage."
to be in for something - to be going to experience something unpleasant very soon
The weather forecast says we're in for heavy rain this evening.
You'll be in for it (= she will be very angry) if you don't do what she tells you. (CALD)