Of course it was a dream.

The nurse was a dream-nurse, who wanted to make him believe that she was real.

But she was not clever enough.

The best way to pay her out for her deception was to take no notice of her whatsoever.

So comforted, he would go to sleep.
At last one morning he woke, a miserably weak but perfectly sane man, and he turned his head from side to side and looked wonderingly at the fresh and exquisite room.