We must be there before the curtain rises.

You must see her in the first act, where she meets Romeo." "Half-past six! What an hour! It will be like having a meat-tea, or reading an English novel.

It must be seven.

No gentleman dines before seven.

Shall you see Basil between this and then?
Or shall I write to him ?" "Dear Basil! I have not laid eyes on him for a week.