You just keep mum about it.

All along I've been wanting to be a robber, but I knew I'd got to have a thing like this, and where to run across it was the bother.

We've got it now, and we'll keep it quiet, only we'll let Joe Harper and Ben Rogers in--because of course there's got to be a Gang, or else there wouldn't be any style about it.
Tom Sawyer's Gang--it sounds splendid, don't it, Huck ?" "Well, it just does, Tom.

And who'll we rob ?" "Oh, most anybody.

Waylay people--that's mostly the way." "And kill them ?" "No, not always.