To save appearances

to preserve a fair outward show.
to preserve a decent outside; to avoid exposure of a discreditable state of things.

See also: Appearance, Save

References in classic literature ?
But I was, what is called, putting it on, to save appearances, though the attack was a genuine one.
The sight is worth some little apprehension; for of real danger there is none, I will go with you and Miss Grand, however, to save appearances.
To see something that was Henrietta, and that is a thing we must cast out and hide, with a little superstitious mumming to save appearances.
I could not tell the others of the day's discovery till we were alone, so after dinner, followed by a little music to save appearances even amongst ourselves, I took Mina to her room and left her to go to bed.