Carolyn Wells 
Come Back 

After his son, Peter, is lost and presumed dead in the wilds of the Labrador coast, Benjamin Crane turns to spiritualism for solace and comfort. So profound is his belief in the medium, that he writes a successful book about his experiences. But when one of his son’s companions on the ill fated expedition is poisoned, at least some of those surrounding him begin to question the honesty of the medium, Madame Parlato. To find the murderer, the famous detective Pennington Wise is called in and it falls to him and his unusual assistant, Zizi to solve the crime and reveal the true fate of Peter Crane. (goodreads)