When waterman Gaffer Hexam (Julian Somers) and daughter Lizzie (Rachel Roberts) fish a battered corpse from the Thames, it is identified as that of John Harmon.
Had Harmon lived, his father’s will required him to marry pretty Bella Wilfer (Zena Walker). Instead, the substantial estate passes on to Mr and Mrs Boffin (Richard Pearson and Marda Vanne), a kindhearted couple who adopt Bella. The mysterious John Rokesmith (Paul Daneman) becomes their trusted secretary, and they engage one-legged schemer Silas Wegg (Esmond Knight) to entertain them with nightly readings.
Lizzie is pursued by two suitors in the shape of work shy barrister Eugene Wrayburn (David McCallum) and wily Bradley Headstone (Alex Scott), and they become bitter rivals.
But what of Rokesmith’s true identity? And can the course of love and destiny run smooth?