This modest Hammer horror film is really more of a psychological thriller, and although it came right on the heels of Bette Davis' well-known crazy-person roles in What Ever Happened to Baby Jane? and Hush ... Hush, Sweet Charlotte, Davis actually tones down the crazy for her role here as a homicidal nanny. Davis' nanny (referred to merely as Nanny) ultimately comes off as damaged and pathetic rather than evil, although it takes the movie a long time to get around to offering insights into her behavior. Until then, The Nanny is dull and plodding, with little suspense for a so-called thriller.
It's obvious from the start that Nanny is the real culprit in the supposedly accidental death of little Susy, for which her brother Joey has been blamed. Joey steadfastly maintains that Nanny is out to get him, and he's clearly telling the truth. So we sit through Joey's parents accusing him of crying wolf, and Nanny looking deceptively innocent, when the real truth of the situation is never in question. William Dix is quite good as young Joey, who spent two years at a school for troubled kids after his sister died and is now horrified to find Nanny still inhabiting his home. But Joey is a brat who doesn't seem too concerned with the alleged murderer living in his house, even as he works to protect himself. He just kind of mopes and whines until Nanny cracks.
And when she does, the movie actually displays some startling sensitivity and social realism, and Davis doesn't oversell it. There's a real sadness to watching Nanny grieve, and the depiction of the aftermath of a back-alley abortion is stark and jarring. Too bad it comes after all that desultory pseudo-suspense, and leads only to unhinged ranting. Those little moments of sympathy just aren't enough.