The unclued lights are trios of Cluedo © rooms at 1A, 14A and 40, weapons at 6, 13 and 14, and suspects at 5, 27 and 36. The solution to the crime are the highlighted HALL, ROPE and PLUM.
 
First prize P. Langdale, London N11
Runners-up Matthew Cawthorne, Watford, Hertfordshire; Barry Fisher, Bramhall, Stockport