"She would not have had time to change the key from the inside to the outside," mused the Inspector. "I daresay the key all along was on the outside, as it is now." He glanced at the door leading into the back room, and sure enough there was the key. "Possibly, she shot the bolt--there is one on the hither side of the door, as I noticed. Well?"
"Well, while I was filling the tank of my car with petrol she must have emerged, and--as you say--unable to escape without observation by the road, she must have slipped upstairs. When I found the door open on trying it for the second time, I entered the back room, attracted by the last moan of the dying woman. Then she--the murderess, I mean--must have come down, and after softly turning the key, have gone off in my car."
"But why should she leave the car in a field?" asked Cannington.
"To the more easily escape," said Dredge, raising his eyebrows. "A car with a number could easily be traced. She took it as near Murchester as she dared, then abandoned it, and walked to the town. That is my theory, and then she could either remain in Murchester or take the train to some other place. It will be a hard matter to find her, as she has concealed her trail very successfully."
"She might have left some evidence behind in the car," I suggested.
Dredge shook his head. "I examined the car myself this morning," he remarked. "There is not a vestige to show that any woman occupied it. She has not left even so much as a pin behind."
"Pardon me; she left a hat-pin!"
"Yes," said the Inspector grimly, "in the heart of the unfortunate Mrs. Caldershaw. But your car is still in that field near Murchester, Mr. Vance, and I shall leave you to take it away. I don't know how much it is injured."
"Last night you said that it wasn't much hurt," I said hastily.
"Quite so, sir," said Dredge imperturbably. "But last night my examination was necessarily perfunctory, as I was in a hurry to reach the scene of the crime. This morning I examined the car more carefully, and I am not sufficiently an expert to see what damage has been done. Remember, it was driven violently through a wooden gate."