Wikipedia
Companion Piece is an original novella written by Robert Perry and Mike Tucker and based on the long-running British science fiction television series Doctor Who. It features the Seventh Doctor and Catherine. It was released both as a standard edition hardback and a deluxe edition (ISBN 1-903889-27-8) featuring a frontispiece by Allan Bednar. Both editions have a foreword by Colin Midlane.
Usage examples of "companion piece".
Let me keep Lady Elene alive, as a hostage, a companion piece to Princess Blessing.
It was not until we had almost reached the cemetery, near which there was a second siding, that another car moved up clanking and tinkling behind us, and soon its companion piece, which we had long seen waiting in the mist up ahead, its yellow light shining wet in the fog, started up and passed us by.
For example (as a companion piece to the story of the Baudi twins) let me mention a Delhi beggar‑.
It hung with a companion piece, a curl of hair embedded in a plastic pendant.