Ambassador Sarek has been on board the Enterprise 1701-D and has been exhibiting some very un-Vulcan behavior.
Picard: I saw you crying.
Sarek: I do not cry.
Picard: I was there, I saw the tears.
Sarek: You exaggerate, Captain. I recall only one tear.
The number of tear is not in question. Whether it was one, or 1,000 Vulcans of Sarek’s stature and experience do not express emotion. Sarek’s being moved by the music is a strong indicator something is amiss.
Strange things are happening to a passenger, Amanda, aboard the 1701-D. Q suspects Amanda might herself be a Q, so he tests this theory …
Troi’s quite reasonable question “what would have happened was out of concern for the ship and its crew. But Q, self important as always, can only see how the outcome of this test effects him.