Goofs

When Holmes breaks the glass to get back inside the train, the broken glass is different between shots from inside and outside of the train.

When Holmes is sitting by himself in his compartment, he is leaning against the back rest and the suitcase is next to him. However, in the next immediate cut when Watson enters and Holmes tells him to leave the door open, he is now leaning forward and the suitcase is not next to him. Then in the next cut, he is back to leaning and the suitcase is again next to him.

Early in the movie the discovery of the Star of Rhodesia is shown. The diamond picked out of the mud looks perfectly clear, with sharp edges. However, raw diamonds have rough round edges and appear quite ordinary, with only a hint of regular crystal form.

About 10 minutes in the, obviously model, train travels at breakneck speed around a sharp bend in the double track but is travelling on the right hand track. Trains in Great Britain on double track travel on the left hand track, except in emergencies. The train is thus travelling on the wrong track which, when genuine, is known as travelling "wrong line".

The police would not arrest a suspect and escort him from a train with a coat over his head.

About 50 minutes in, the train stops at a station, obviously hauled by a foreign engine, rather than a British one, and leaves the same way. This engine error is seen several times throughout the film.

About 40 minutes in, people in a compartment are told that they will have to stay on the train until it reaches Edinburgh. A London to Edinburgh train would leave from Kings Cross Station and travel via the East Coast Main Line, operated then by the London and North Eastern Railway (LNER). At the start, the train is shown as one of the London Midland and Scottish Railway (as evidenced by the "LMS" abbreviation on the carriages). LMS expresses left from Euston Station and traveled via the West Coast Main Line to Glasgow, not Edinburgh.

Renee Godfrey (playing Vivian Vedder) seems to struggle with her British accent as an American actress.

The exterior shots of the train show different trains, including a model and a continental locomotive. At various times running wrong track on double track lines (UK runs on the left); numbers of carriages increase and decrease; carriage livery incorrect for LMS in 1946 (or earlier), should be LMS single colour "crimson lake"; one carriage seems to be all white (and disappears later); an overhead shot of clerestory roofed trains running wrong track, whilst all the other views are arc roofed, whether model or interior shots.

The train is traveling at a high rate of speed however the inside of the train is still, and the passengers are walking and sitting normally. The only time there is any inside indication of a moving train is when the empty stool that the sleeping guard was sitting on is shown rocking back and forth.

When the villain leaves the unconscious Inspector Lestrade in the railway carriage, the curtains over the door are not closed all the way across, but when Holmes and Watson return to the carriage, the curtains are completely closed.

Lestrade's passenger list gives the forename of Lady Carstairs' son as Roland; however some time later in the guard's van, Holmes refers to him as Ronald.

When Moran shoots his accomplice, he uses a handkerchief to wipe his fingerprints off the gun however he turns off the light in the compartment without using the handkerchief to prevent leaving his fingerprints on the light switch.