Sentence:  Ismay and Heather share a festering secret that poisons more than one relationship in this London household before seeping out and infecting all the neighbors — including the <WSD>homicidally</WSD> inclined Marion and her abominable brother, Fowler, who have made a career of preying on the love-starved. 
Meaning of the word marked with <WSD> tags:  In a homicidal manner.