Three Witnesses: a Classic Crime Novel

Roger Truscott and brother Cyril inherit a controlling interest in their late father's firm. Rowton, the company manager, urges them to sell out before the business fails. The brothers argue in Rowton's office, and shortly thereafter, Cyril is shot dead on the entrance stairs. Three witnesses claim to have seen the brothers together at the exit. Is Roger doomed to hang, or can a police inspector, young solicitor, and attractive typist unravel this complex mystery?