The Mystery on the Miniature Railway

Professor Mark Hills boarded the Romsey, Heath and Little Church Railway to view the terrain on route to Downsend Nuclear Power Station. He was on his way to give a presentation of his new Nuclear Waste Reprocessing System - a revolutionary way of creating electricity out of nuclear waste, leaving harmless residue. But when the miniature train arrives at Downsend the last carriage, where the Professor was seated, is empty...