Later, a pistol, which is mine, is found in the lady's work-basket, hidden under repairing material.

The first suggestion is that Miss Rider is the murderess.
That suggestion is refuted, first by the fact that she was at Ashford when the murder was committed, unconscious as a result of a railway accident; and the second point in her favour is that the telegram discovered by Lyne's valet, purporting to be signed by the girl, inviting Lyne to her flat at a certain hour, was not delivered to the murdered man." He rose to his feet.
"Come along and see Cresswell," he said.

"This case is going to drive me mad!" Assistant Commissioner Cresswell heard the story the two men had to tell, and if he was astounded he did not betray any signs of his surprise.
"This looks like being the murder case of the century," he said.

"Of course, you cannot proceed any further against Miss Rider, and you were wise not to make the arrest.

However, she must be kept under observation, because apparently she knows, or think she knows, the person who did commit the murder.