They Do It with Mirrors

S4 E3: Miss Marple's old friend Carrie-Louise has always had a soft heart for charitable causes. This time it's juvenile criminals, lodged in a reformatory on her estate. But her sister, Ruth van Rydock, is worried about her and asks Miss Marple to pay a visit. With her sharp eyes and unerring sleuthing skills, Miss Marple quickly assesses the situation-but not in time to prevent a murder. Can she save her friend from becoming the next victim?