As the story opens, Stratford Harlow is on his way to meet solicitor Franklin Ellenbury in Devon. Harlow sees a convict working party returning to Dartmoor Prison and on a whim decides to go back to the hotel he has just left and summon Ellenbury to come to him. We know right away who else is on the wrong side of the law, since Harlow instructs Ellenbury to pretend they are strangers when they meet at the hotel. Ellenbury cannot refuse this or any other summons, for Harlow has helped him pay debts and replace money embezzled from clients. Indeed, Ellenbury is still receiving money from Harlow in payment for his participation in certain of Harlow's financial dealings.
By changing his plans and returning to the hotel Harlow notices and eventually scrapes up acquaintanceship with Aileen Rivers. She's on her way to visit her actor uncle Arthur Ingle, now doing a stretch in Dartmoor for forgery and fraud.
Harlow, a multi-millionaire, is an unusual rogue. He enjoys his "jokes" -- many would call them criminal -- no end, so it's not surprising the name of Sub-Inspector James Carlton of Scotland Yard comes up in conversation between Harlow and Ellenbury. Several months later, in typical Wallace fashion, Carlton meets Miss Rivers by accident (literally) on the Thames Embankment. Fortunately she is only shaken and her elbow slightly injured, but he insists on escorting her home.
Miss Rivers is looking after her uncle's flat while he's in durance vile and when it is burgled she calls Carlton for help. While he's there, Harlow shows up out of the blue to offer her a job or so he says, but suddenly faints and when recovered leaves in a hurry. Carlton has his eye on Harlow, but the latter has covered his tracks so well it looks highly unlikely Carlton will ever be able to pinch his prey.
What follows is a gallop through a plot featuring a couple of laugh-out-loud moments, burglary, a man held a prisoner in luxurious surroundings, underground rooms, a sinister housekeeper, fortunes made and lost, and strange goings-on in the House of Commons, among other shenanigans.
My verdict: Stratford Harlow is one of those engaging villains readers feel they should boo and yet there is something charming about him, as Miss Rivers freely acknowledges. Wallace engages in some wonderful misdirection and while his characters and situations are in true detective fiction fashion not always what they seem, he manages his literary sleight of hand so well readers will almost certainly be surprised when at the end of the novel they learn...well, I won't say what. Read it and find out!