Having destroyed three of four Rutan craft encountered in the Sol system, Commander Churl pursues the fourth damaged craft down to Earth, accompanied by Lieutenant Stavv. The Rutan craft has crashed on a remote farmhouse, killing one woman when the roof collapsed and leaving a male dead from a surviving Rutan's attack. Leaving Stavv to retrieve information from the Rutan science ship, Churl pursues his hunt. He encounters a blind girl. Dismissive at first, the girl directs him to a barn which turns out to be empty. In a moment, Churl loses the girl and returns to the Rutan craft.
Stavv is not there. The terminal he was using displays files for the Metamorphosis Technique, a new, flawed technology to enable a Rutan to assume a body copy from a tissue sample. It usually creates a flaw, a disability distinct from the original copy, nor can the shape be held if the Rutan kills its prey with its 'electric' sting. Returning to the farmhouse, Churl meets Stavv, who is dragging a wounded leg. Stavv declines Churl's offer to use the tissue rectifier, preferring to carry the scars as a badge of honour and bravery and a reminder of being beaten.
With Churl in the middle, the Sontarans face the blind girl at the farmhouse. She has armed herself with a gun. Stavv realises he must choose quickly which is the Rutan copy. He fires the tissue rectifier at the girl, which restores her eyesight. She points her gun at the Sontarans and sees "Stavv" revert to his Rutan form. Churl moves aside; the girl fires and kills the Rutan responsible for her father's death. Churl explains a real Sontaran would only carry wounds as a mark of victory in battle; other wounds would be healed in preparation for the next battle. Churl commends the girl for avenging her family with honour and asks her to bury the body of his lieutenant with due ceremony when he has gone. With the girl watching, Churl leaves in his scoutship to rejoin the war.
- This story makes reference to several Sontaran technologies, namely scout ships, tissue rectifiers and the Sontaran translation unit.
- The ongoing Rutan-Sontaran War is an established Doctor Who storyline.
- The Metamorphosis Technique in its early flawed development stage was a central theme in the only televised Rutan story, TV: Horror of Fang Rock.