Through the window he had seen an open door behind Rann, and his blood thrilled with the idea that had come to him.

He was sure the two partners in crime were discussing himself and MacDonald--and Joanne.

To hear what they were saying, to discover their plot, would be three quarters of the fight won, if it came to a fight.

The open door was an inspiration.
Swiftly and silently he went to the rear of the house.

He tried the door and found it unlocked.