She tightened the screws, threw the main isolator, and the lights flickered back to normal. The hum stopped. The radar dish went still.

“Aye, mum,” Callum said, throwing the main isolator. The hum of dying fluorescents faded, and the only sound was the sea hammering the rocks fifty meters away.

“The logbook,” Eilidh said, slipping the yellowed note into her breast pocket, “will record a successful service of the existing Hager BP10140. No anomalies.”

“No,” she said, shoving the old breaker back onto the rail. “We’re not replacing it. We’re not fixing what isn’t broken.”

The culprit was a black, rectangular box mounted on a DIN rail. Its faded label read: .

Callum had already connected the supply sense wires. “Ready for the new one, boss.”

She made her choice.