The Fallen Idol is a morally complex story about the loss of innocence, and the nature of lies seen through the eyes of a child, the wonderful Bobby Henrey, who speaks both French and English and delivers one of the most natural performances of a child in film. Some people find him irritating; I think he is adorable. Inquisitive, needy of attention, but sweet and goodhearted (not all children are). He plays the son of the French ambassador to England, a neglected, motherless child living alone in a huge mansion, in the company of his butler, Baines, the inimitable Ralph Richardson (looking a bit like Kevin Spacey, I dare say).
Baines is the butler we all would want if we could have a butler, infinitely crisp and efficient and wonderful. He is married to a horrid housekeeper, portrayed to the hilt of evil by Sonia Dresdel (beware of people who clean too much). Thus, he is in love with Michele Morgan, a secretary at the embassy and possessor of most amazing cheekbones. So Baines, who is a hero to his charge, is a liar. And the child, due to his loneliness, somehow gets enmeshed in the adults' web of lies. This is a world in which there are many kinds of lies, from sins of omission, to actual enormous lies, to tall tales of courage in Africa. Point is, the kid can't tell the difference between one lie and another.
Graham Greene said he converted to Catholicism because "I had to find a religion to measure my evil against" (how fun is that?), and so his enduring themes are those of man's fallen nature, of innocence and and evil, free will and redemption.
But being a novelist, not a saint, Greene multiplies the ironies. The lovers are kind people who care about the child, even if they are committing a sin. Mrs. Baines is their victim, but she is an awful human being. The poor kid is caught in the middle, actively trying to make sense of this complicated world, in which he has been made to feel responsible.
The intimation of unwitting (on the part of Baines) cruelty to the child is very hard to stomach. Everything converges on the vulnerability of this child and on how he has been tainted by the adults' mistakes. Meanwhile, if this assessment makes the movie sound like Catholic Dogma 101, it isn't. There is nail biting suspense, ironic twist after ironic twist, amazingly sharp humor, and the most riveting, suspenseful, and comical scene involving a little paper plane.