They Mostly Come Out At Night

Mummy Holmes was admiral of the British space fleet, and her sons were gestated in a synthetic womb called an AGU. When something monstrous burst out of a lieutenant's chest and got loose on board a ship carrying the Holmes family, the unborn second son and was left on board.
A quarter of a century later, the Orbiter 200B is a floating wreck on the edge of the colonised territory. Mycroft Holmes sends Lestrade and a Royal Navy special ops vehicle, the Baker, to the abandoned ship to learn what can be salvaged.