gap

“It fills up a gap which I had been unable to bridge in this most complex affair.

Finally, his eyes came round to the fresh and smiling face of Billy, the young but very wise and tactful page, who had helped a little to fill up the gap of loneliness and isolation which surrounded the saturnine figure of the great detective.

With five volumes you could just fill that gap on that second shelf.

“I have not seen a man who, if he turns his talents that way, was more calculated to fill the gap left by the illustrious Moriarty.