Donna Leon - Season 1 Episode 7 Quietly in Their Sleep

Brunetti comes to the aid of a young nursing sister who is leaving her convent following the unexpected death of five patients. At first, Brunetti's inquiries reveal nothing amiss, and he wonders whether the nun is simply creating a smoke screen to justify abandoning her vocation. But perhaps, she has stumbled onto something very real and very sinister - something that puts her life in imminent danger.