The green light

de Louise Landon, Grosset & Dunlap, Penn Publishing Company

"She never knew what it was that wakened her. She found herself sitting up in bed, her heart racing furiously, her mouth dry with fear. There was a menace in the silence, a threat in the darkness. As she sat there, rigid, save for the heavy breaths which shook her, the girl knew that an alien presence was near. She stole to the door, opened it. At the far end of the hall a faint green light flickered for an instant, then disappeared. It was the beginning of a week of ghastly events which culminated in a murder frankly baffling to the police. it needed a former crack newspaper reporter to solve the mystery and follow the weird green light to its unbelievable source" -- from dust jacket.