The Barton Tunnel Mystery by Hal Meredith

Barton Tunnel is some six miles from Merriton on a small single-line railway linking up Merriton with the main system, which it joins at Fulchurch Junction. There is a train which leaves Merriton at 4.20 p.m. and arrives at Fulchurch at 4.40. When it drew into that station yesterday afternoon, a guard, on opening the door of a first-class smoker, was horrified to discover the body of a well-dressed, middle-aged man lying in a huddled heap on the floor near the farther door, the window of which was down. Sexton Blake investigates.