So Richard Poole is out, Humphrey Goodman is in. Killing off the main character in a light-hearted mystery show is a long way from ideal, and I must admit I was surprised. They had a perfectly good excuse for Richard to leave at the end of Series 2, which would have rounded out his and Camille’s arc nicely. But perhaps Ben Miller pulled out after those scenes had been finalised. If that’s the case, then I think they’ve done the best they could with a very difficult situation. The new detective seems an amiable enough chap, and the soap opera is so low-key that I expect after a few episodes Richard Poole will be entirely forgotten. In fact, it’s probably a good thing that Poole is gone, because there wasn’t really anywhere sensible left to take the relationship between him and Camille.

The puzzle, as usual, was a reworking of Agatha Christie techniques. Although the trappings were Cards on the Table – with a focus on motive and opportunity rather than psychology – the real meat of the case was taken from A Murder is Announced (sister steals identity to claim fortune, undone by unfortunate run-in with a person from the past).

I thought the initial scene was particularly clever, tricking the viewer into thinking that Richard’s discomfort was due to being a general sourpuss rather than the unpleasant truth that he’d discovered.

The mystery was easy enough to solve, but that’s not a problem. Like any other puzzle, there’s room for a wide range of difficulties. You wouldn’t print a crossword in a newspaper if you thought no-one could solve it. Yet there seems to be a common misconception that a mystery has to be baffling and surprising to be successful. While that’s one way to write them, there’s no reason why a mystery shouldn’t be designed to be easy, and in fact very difficult mysteries are much simpler to write, provided you don’t mind annoying the audience. Death in Paradise puzzles are designed to be both solvable from very early on and grow easier and easier as the conclusion approaches. That’s a tricky thing to pull off, but I wouldn’t be surprised if it accounted for a lot of the programme’s popularity (viewing figures almost as high as Sherlock). It’s also a good fit for its length. It can be a bit tiring waiting for a mystery to resolve itself if you already know the answer, but an hour isn’t really long enough for that kind of boredom to set in. It would be a lot less successful as a series of books, where even the fastest reader would need to wait several hours to have their theory confirmed.

Still, while puzzle plots have a lot of leeway in terms of difficulty, I think there’s less wiggle room when it comes to consistency and clarity. Death in Paradise always tends to waver a bit here, and this episode was no exception. Here are a few things I’d have pointed out if I was script editor:

Minor Niggles

The solution doesn’t seem to be unique. Why couldn’t James have stabbed Richard when he took the empty cup back out the second time? If you’re going to have these artificial puzzle plots, I think there should really be a single possibility to explain things.

Suggestion: Maybe take James’ prints off the ice pick. He was shown drinking beer rather than cocktails. Adds to the impossibility, and shows why it’s essential for him to establish an alibi for Helen.

The evidence about the saliva in the teacup is a little confusing. I assumed that meant there were two separate cups, one for each time Richard was supposedly brought some tea. But the solution showed the same cup was used both times. But then why couldn’t it have been refilled and then poured away, undrunk, by the killer? Richard’s saliva could still have been in the cup from the first time. Clues like this don’t need to be forensically accurate, but it should be clear to the audience what rules they’re imposing on the puzzle.

Suggestion: I think there should maybe have been one more run through of exactly what was supposed to have happened on the veranda. Normally Death in Paradise repeats the rules of each week’s puzzle every ten minutes or so, even when it isn’t really necessary. It seems odd to change that pattern the one time there’s a genuinely complicated setup.

Sasha’s physical transformation into Helen seems to be stretching things a bit, even given the span of time and the fact they were sisters. (Having basically solved the puzzle, but missed the thing about them being in different years, I assumed the photo album was going to reveal that they were twins.) As so often in mysteries, “cosmetic surgery” seems to be shorthand here for “perfect identity change magic”.

Suggestion: Maybe make it more obvious that Helen/Sasha has survived a bad car crash? It’s tricky to get this balance right on TV. For the clue to go unnoticed, “cosmetic surgery” has to seem like it refers to a nose- or boob-job. In a book you could just gloss over Helen’s appearance.

More Problematic:

Why did Helen and James agree to the reunion at all? Even without knowing Richard would be there, it seems an incredibly risky thing to do. After all, it would be natural to relive stories from when they were at university, and Helen would be likely to make all kinds of mistakes.

Suggestion: See below.

What about everyone else? Yes, Richard knew Sasha better than the other two guests at the reunion, but what about Helen and Sasha and James’ other friends? What about their families? Didn’t they meet anyone else between university and the car crash? The story seems to be happening in a vacuum.

Solution: I think the best way to fix these problems would be to address them both at once: Helen and James need to escape because people at home are suspicious, and the reunion would provide a convenient and plausible excuse to get out of the country quickly before heading somewhere else.

Most Problematic:

Why did Richard stay there to be killed? Richard was established over the 16 previous episodes as intelligent, risk averse and unbothered about causing offence. Why wouldn’t he just leave once he’d proven to his own satisfaction that Sasha was Helen?

Solution: Not sure. Perhaps make more of the taxi Richard arrived in? Presumably he’d arranged a pick up time and that’s why he was forced to wait. It’s still not ideal (if Richard was that suspicious of a crime it seems unlikely he wouldn’t have confided in one of the others and brought them along to make an arrest then and there).

Even this isn’t a massive issue. Unlike some of the problems I have with, say, Sherlock, the episodic nature of Death in Paradise means it’s hard for issues like this to cause lasting problems beyond the immediate storyline. Still, I think the potential to run into difficulty here is worth bearing in mind for people who write mystery series where there’s an on-going cast of characters involved in sub-plots which are separate from the cases (cosies seem especially likely to fall into this category). No-one on the mystery side of Death in Paradise behaves very sensibly, but that’s fine because they’re basically puzzle pieces and it’s a whole new batch of implausible behaviour every week. With five new characters over an hour-long episode there isn’t much time to form opinions.

The main characters do behave realistically for ongoing soap-ish storylines, but the two halves of the programme are kept separate (pseudo-exceptions: one of Camille’s friends was murdered, Dwayne was briefly a suspect, Catherine’s new boyfriend was a murderer. But this is the first time a main character has seriously been involved in a case). Transplanting a character completely from the soap half to the mystery half creates problems, because there are now mismatched expectations on how they’ll behave.