More unlikely things had happened.

What if the water were poisoned or drugged?
He placed the tin to his lips.

The liquid was musty, having been in the skin nearly two days.

Otherwise it seemed to be all right.

With a sigh of profound relief he gave Iris the cup, and smiled at the most unladylike haste with which she emptied it.
"Drink yourself, and give me some more," she said.
"No more for you at present, madam.