His friends should be sent for.

Do you know anything about him?
Is he staying at the hotel alone?
I only arrived here last night." "I believe he is staying at the hotel alone.

He has been here for a fortnight or more, and I have never seen him speak to anybody, though I have exchanged nods with him every morning.

His principal recreation seems to lie in taking long solitary walks along the coast.

He has been in the habit of going out every day, and not returning until dinner is half over.