The Shadow of the Past by Ethel Mills

Abruptly Matheson dropped the lid, faced about and looked up. The sensation of being observed, of not being, for all that the hut appeared to be empty, alone, was explained. Some one -- he had no means of knowing who -- was familiar with Nel's secret. Whoever it was, it appeared very certain that he was at the moment watching him from the room above, was aware moreover through his incautiousness that the hiding place was equally well known to the man who stood staring up at the movable thatch in amazed and thwarted curiosity.

To Matheson it was the most astonishing and perplexing moment in his life. He remained riveted to the spot staring, staring helplessly at the innocent-looking grass roof, trying to discern the intruder; seeing no one and hearing no sound of movement, yet acutely aware that some one lay concealed in the roof, some one who had thought to hide from him, who was undoubtedly even then observing him, secure in the knowledge of remaining himself unseen.