Edgar Wallace 
Square Emerald [PDF ebook] 

‘Suicide on the left, ‘ says Chief Inspector Coldwell pleasantly, as he and Leslie Maughan stride along the Thames Embankment during a brutally cold night. A gaunt figure is sprawled across the parapet. But Coldwell soon discovers that Peter Dawlish, fresh out of prison for forgery, is not considering suicide but murder. Coldwell suspects Druze as the intended victim. Maughan disagrees. If Druze dies, she says, ‘It will be because he does not love children!’