Who are the suspects in Shetland? Here's everything we know so far

...three dead bodies, multiple young women held captive, a guy in hospital with serious stab wounds, and now another guy who may or may not be dead.

Luckily, DI Jimmy Perez (Douglas Henshall) is on the case and he's determined to get to the truth.

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So what is really going on – and who is guilty? Here are all the key people involved and what we know about them so far...

Zezi's jailor 'Paul Kiernan' (John Kazek)

What do we know about Paul Kiernan? Firstly, we know that his name's not Paul Kiernan: he's actually a Glaswegian called Adam McGuire with multiple convictions for fraud and an assault charge to his name.

Secondly, we know that he is DEFINITELY a bad guy. 'Paul Kiernan' is heavily involved in the trafficking of victims including Daniel's sister Zezi and the girl with the butterfly tattoo on her wrist. This man moved these girls from the MacBay Hotel on Shetland to another unknown location, most likely using Calum's boat the Silver Darling to ferry them to the mainland.

We also know that he is cruel and violent, taking pleasure in taunting Olivia about her son Daniel's death – and later threatening Zezi by grabbing her by the neck.

What we don't know is whether he is responsible for the murder of the Hayes family, or why he would have killed them. Perez previously saw 'Paul' and Prentice Hayes arguing at the MacBay but they seemed to have made up by the time he left.

We are also in the dark about who he is working for – after all, he's unlikely to be running the whole operation by himself.

Now, 'Paul' has vanished from the MacBay, and from Shetland altogether, so Perez and his team must pay a visit to Glasgow to find out more.

Prentice Hayes (Owen Whitelaw)

We won't hear any more from Prentice Hayes himself, on account of him being dead: stabbed to death at the family home alongside his mother Carla. But what was he up to, what did he know, and how is all this connected?

Prentice was a man with his fingers in many pies, few of them legal. He was renting out caravans to young sex workers on Shetland, and – as Tosh discovered in episode two – was growing an impressive quantity of weed inside one of the family's properties. It seems he also had a role within this trafficking operation.

In episode one, Perez established that Prentice knew about Daniel poking around at the caravans before he was killed. In fact, Prentice actually told the girls working there not to say anything about Daniel to anyone, so he must have had an idea about who this boy was.

Another coincidence: he had recently bought the chemical used to partially-dissolve Daniel's body.

Perez also noticed Prentice hanging out with Paul Kiernan, and has found a connection between him and fisherman Calum going back at least two years. As viewers, we know that Prentice recently summoned Calum for a little chat which wasn't entirely friendly.

So who went to kill the Hayes family, and why? Could Paul Kiernan have done it before escaping on the Silver Darling, or was it someone else? Did Prentice know too much? We're still connecting the dots.

Jamie Hayes (Lorn MacDonald)

It's worth mentioning Jamie, the sole survivor of the stabbing at the Hayes family home.

Prentice's brother, Jamie only narrowly escaped, making it to his car where he almost bled to death from his wounds. At this point Perez doesn't think he has anything to do with Prentice and Carla's murders, especially as he was so badly injured himself.

But there's something funny about his story. He describes the assassin as an unidentifiable man in a balaclava who didn't say a single word – ie he is completely unidentifiable. Does young Jamie know more than he's letting on?

Daniel's mum Olivia Lennox (Rakie Ayola)

Olivia seems not to have murdered the Hayes family after all: her claim that she only got to their farmhouse after they were already dead appears to be true. But she's also a bit of a wildcard in the story and there may be more about her family history (or what happened at the Hayes house) that she is not telling the police.

Fisherman Calum Dunwoody (Ryan Fletcher)

We know Calum was involved in some very dodgy stuff – although most likely he was a cog in a much larger machine. Unfortunately he managed to stab himself before the police got the full truth out of him, so (for the time being) he won't be talking.

Calum did admit to transporting a whole bunch of people in the hold of the Silver Darling, taking them under the cover of night from Shetland and landing them on Scrabster on the Scottish coast. But he wouldn't give the police any names or identify any passengers, insisting "You just do what you're told, you don't ask these guys any questions."

Left alone in a cell with a pen and paper, he stabbed himself in the neck (presumably very painfully) with a biro. Calum clearly feared his wife and kids would be harmed if he betrayed whoever he was working for, so there must be some Very Scary People running this thing.

To his credit, it doesn't sound like Calum was a particularly willing participant in this whole scheme. He was not pleased to be approached by Prentice, and he told an unknown caller down the phone: "I did my job, you sort it out yourself."

One final detail to note: Daniel was seen giving the Silver Darling a once-over shortly before his death, so he must have had some clue about this boat's involvement in his sister's disappearance. What did Daniel find out and how? Perez will have to uncover more about this, with or without Calum's help.

Tosh's love interest Donnie (Angus Miller)

Okay, so this Donnie lad hasn't actually done anything bad (that we know of), and there's no evidence against him at all. But isn't it a bit... convenient... that he turned up to woo Tosh out of the blue?

And wasn't that a knowing look from Prentice at the bar when Donnie introduced himself to Tosh?

We should really say "re-introduced," because Donnie claims that they met before, at an exhibition last year. Except Tosh has no recollection, despite being an excellent detective who usually remembers every little detail.

This is wild speculation, but could he have been assigned specifically to seduce Tosh and get the inside scoop on the investigation?

An international human trafficking operation

A lot of the evidence points towards a much, much larger story stretching well beyond Shetland. Calum, Prentice and 'Paul Kiernan' were clearly involved in this whole sinister business, but we may not have even met the "big bad" yet.

"A stop to it? Have you got any idea who you are dealing with here?" Calum warned Perez across the interview table. "This thing is huge. These people are everywhere. You? You're just some guy standing on a rock in the middle of the sea."

He may well be right.

Shetland continues on Tuesdays at 9pm on BBC1

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