Mary Roberts Rinehart's mystery book

Three of Rinehart’s pre-WWI mysteries, all best-sellers in their day. Reviews from Goodreads. The Circular Staircase – (Wealthy spinster Rachel Innes gets mixed up in a series of strange crimes at a summer house she has rented with her niece and nephew). “For twenty years I had been perfectly comfortable; for twenty years I had had the window-boxes filled in the spring, the carpets lifted, the awnings put up and the furniture covered with brown linen; for as many summers I had said good-bye to my friends, and, after watching their perspiring hegira, had settled down to a delicious quiet in town, where the mail comes three times a day, and the water supply does not depend on a tank on the roof. And then -- the madness seized me. When I look back over the months I spent at Sunnyside, I wonder that I survived at all. “ The Man in Lower Ten – “Lawrence Blakely, an attorney-in-law carrying important papers, stumbles on a murder aboard a train. Meanwhile, his bag containing the valuable documents has been stolen, along with his clothes, and he's being accused of the killing when the train is wrecked. Blakely and a mysterious young woman may be the car's only survivors.” The Case of Jennie Brice “A blood-stained rope and towel, and a missing tenant, convince Mrs. Pittman that a murder has been committed in her boarding house. But without a body, the police say there is no case. Now, it's up to Mrs. Pittman to ferret out the killer. For as the landlady, she has the perfect excuse to do a little snooping--and the key to Jennie's apartment.”