'There,' said Reggie triumphantly, 'did you see what a bad conscience he has?' and they all looked at each other in silent assent.
Declining Mrs. MacAlister's invitation to stay to tea, they trooped out of the post-office.
'We'll watch that man,' said Reggie, and Tricksy began to walk on the tips of her toes in anticipation.
'Hulloa, young people, glad I've overtaken you,' said the doctor's voice behind them. 'It's just going to pour with rain, and you're due at my house to tea, I believe. It's lucky I have the closed carriage; jump in as many of you as it will hold, and the rest of you can sit on the box.'
By the time the doctor's house was reached the rain had stopped, and the sun was peeping out again. A scrap of white paper fluttering on the ruins attracted Reggie's attention, and he ran across the garden, climbed the wall, and captured it.
After looking at it he gave a violent start, then ran towards the house.
'It's a postal order,' he said, giving it to the doctor; 'what's the meaning of this?'
All clustered round, and the doctor took the piece of paper and examined it.
'Strange thing,' he exclaimed; 'this order bears the number of one of those that went missing on the night of the robbery. How did it come there? It's wet with the rain, but not very dirty; probably hasn't been there long. This ought to shed some fresh light upon the case. I'll have the police to make a thorough search of the ruins.'