It looked like a beautiful, long letter.

It was quite thick.
But when she had opened it, she saw that the letter itself was not very long.

Several extra sheets of notes or instructions, it did not matter what, seemed to be enclosed.

Her hand shook so that she let them fall on the floor.

She looked so agitated that Jane was afraid to do more than retire discreetly and stand outside the door.
In a few minutes she congratulated herself on the wisdom of not having gone downstairs.