The characters in River have a bleak quote for every occasion

But where do the quotes come from? Two episodes in, it's time to dig out our book of proverbs.

“Do not go where the path may lead. Go where there is no path and leave a trail.”

Episode two began with a special message for Detective John River. These aren't just fortune cookies. These are M&S literary fortune cookies.

The quote is often – wrongly – attributed to Ralph Waldo Emerson. In actual fact, it probably originates from a poem by 20th century writer Muriel Strode.

Now we've started on a trail of our own, what about the other quotes from the series?

"Guilt has quick ears to an accusation"

River's mysterious 'manifest' Cream appears to him as a vision whenever he is at his lowest ebb. The figment of his imagination is based on a real-life killer that River is reading about, murdering Victorian physician Thomas Neill Cream.

Whatever River's unexplained condition is, there's no denying that his 'manifest' Cream is remarkably well-read. The above quote originally comes from Henry Fielding's 1751 novel Amelia.

“It is forbidden to kill, therefore all murderers are punished, unless they kill in large numbers and to the sound of trumpets.”

Another delectably devilish line from Cream, delivered in episode one with serious menace by actor Eddie Marsan. The line was originally written by Voltaire, taking a side swipe at so-called 'justice' in war and what it means to be a killer.

It's bad enough that River is imagining these lines spoken by a serial killer, but it's made much worse when he then repeats them during a police press conference. River is cracking up – and Cream shows just how dark is mind has become.

While we're on the subject of Cream quotes, here's another from the first episode: "Have no fear of robbers or murderers. They are external dangers, petty dangers. We should fear ourselves.”

That's from another French writer and philosopher, Victor Hugo in his great novel Les Misérables, published in 1862. What a well-read figment of River's imagination Cream is...

“Old sins cast long shadows.”

It's not just the characters in River's mind who have a penchant for proverbs. Jimmy, the brother of River's dead partner Stevie, is an ex-con who was imprisoned for decapitating someone. Not a man to mess with.

Now 'reformed', he's almost as erudite as Cream. The Oxford Dictionary of Phrase and Fable tells us this particular quote comes is an early 20th-century saying, perhaps influenced by a line from 17th-century playwright Sir John Suckling: "Our sins, like to our shadows, When our day is in its glory scarce appear: Towards our evening how great and monstrous they are!"

Reckon Jimmy read the source text in jail?

River airs on Friday nights on ABC in Australia