The Million Dollar Bond Robbery

The job sounds simple: take one million dollars' worth of Liberty Bonds across the Atlantic on the Queen Mary and hand them over in New York. Poirot is entrusted with the task, and as far as he is concerned the only real problem is the ship. He does not do well at sea. The rocking, the horizon, the whole business of being afloat is a trial for a man who likes his world level and predictable.

And then, despite every precaution, the bonds are stolen. Cleverly. On a ship where everyone is watching everyone, someone lifts a million dollars in negotiable paper, and Poirot has to run an investigation from a state of mild, uncharacteristic misery. He does it anyway, moving through the passengers and crew: Mr Shaw (David Quilter), Mr Vavasour (Ewan Hooper), Mr McNeil (Paul Young), Philip Ridgeway (Oliver Parker), Esmee Dalgleish (Natalie Ogle), the Chief Purser (Christopher Owen), with Lizzy McInnerny doubling as Nurse Long and Miranda Brooks. Hastings is along for the voyage, cheerful and useless in his usual way, and Miss Lemon is not far off.

Anthony Horowitz wrote it with Agatha Christie, and Andrew Grieve directed. The Queen Mary makes a wonderful setting, all brass and wood, full of people pretending not to watch each other. The period detail is handled well, from the liner's public rooms to the way the money moves, and the episode keeps a holiday lightness that suits it.

The ending is the sort of quiet, logical solution Christie specialised in. And there is a small delight in watching the great detective solve a crime while visibly longing for dry land. He gets the bonds back, the voyage ends, and you suspect the walk down the gangplank is the happiest moment of his whole trip. It is one of the lighter entries in the canon, and all the better for not pretending otherwise.