Vigil: 10 questions we have after episode 4

The episode also ended in extremely dramatic fashion as Amy discovered yet another dead body, while she seems to have found an unlikely ally in Prentice, and there's lots more to discuss about Docherty and Glover as well.

We’ve posed all the big questions we have after Vigil episode four below – read on for a full recap and our theories.

Who is the traitor on board Vigil?

While there were several big revelations during this episode, there's no getting away from the biggest one: there is a traitor on board Vigil, working as a Russian source and aiming to sabotage the submarine's mission. Apart from anything else, this certainly adds even more tension to the already nail-biting series, with Amy now having to race against the clock to root out the bad apple before they can act.

On hearing about the news, the Navy command initially insisted it couldn't be true, claiming that everyone on the submarine had been vetted, but as MI5 agent Jay Kohl pointed out, there are hundreds of sailors and it's not impossible that one person could have slipped through.

But who could the traitor be? At one point was suggested that Burke himself could be the Russian agent – perhaps he was sowing discord on the submarine specifically to undermine the mission. It would certainly be a major twist, but it seems unlikely. Surely he would be in a much better position to sabotage the mission had he properly ingratiated himself with the team, rather than acting difficult from the get-go.

So who was it? There's still not a lot to go on at this stage, but the usual suspects can all be considered – Glover, Docherty, and Captain Newsome. Or perhaps we should be looking at those people who are still new to the boat, in which case we should probably keep our eyes on Hadlow and Prentice (the latter of whom Amy says is now "the only person on the boat I do trust".)

Who killed Jackie Hamilton?

For a while during episode four, there was some suspicion that Jackie, the boat's chef, could be the Russian agent. Only, at the end of the episode, she was found dead inside a food storage cupboard, shortly after Amy had found some evidence of the same toxin that had been used to kill Craig Burke in her bunk.

The most obvious culprit at the moment is clearly Glover, after he emerged at the scene with a protective mask and rather forcefully drove Amy away. But did he actually kill her, or did he simply discover the body first and act quickly to save Amy from something dangerous?

Before her death, we saw Jackie look horrified when she read a mysterious note – the contents of which presumably gives a hint as to who might have killed her. Let's hope Amy can get her hands on the note.

What was Jackie up to?

Even if Jackie's death makes it unlikely that she was the Russian agent, it is clear that she's been up to something. Before this episode, we hadn't learned a great deal about her, beyond the fact that she was particularly tearful at Craig's memorial service and that her son was spending time in prison.

But towards the beginning of this week's episode, we found out her son had suddenly been released, arousing suspicion for Amy when she later learned from Prentice that he had been just one year into a 10-year sentence for drugs charges in Indonesia.

And that suspicion was only heightened when Amy found the evidence of the toxin in her bed. At first Amy took this as evidence that Jackie had killed Craig Burke – suggesting that it could have had something to do with her son – but her death seems to make that unlikely. But what exactly had Jackie been doing that got her killed?

What is Glover's role?

After the revelations about his hidden relationship with Docherty last week, Glover has very much come under suspicion – and he continued to be something of a shifty presence throughout this episode.

He basically admitted that he was being blackmailed by Craig Burke and that he had been asked by him to provide evidence relating to events at Port Havers, denied that he gave him anything and was enraged when Amy suggested he could have played a part in the murder.

Relations between him and Docherty are also very strained now – as we saw in an exchange when Glover claimed that he spoke to captain Newsome simply "to protect" her, but she didn't quite believe him.

Then, at the end of the episode, we got a shot of Glover looking rather concerned when a tannoy announcement called for Jackie Hamilton to report to the control room, before his aforementioned appearance at the scene of the crime. Even if he didn't kill Jackie, he clearly knew something secret about her – otherwise, why would he look so concerned when he heard the announcement?

Who took the comms system down?

The discoveries made over the course of the episode led to the decision to recall Vigil – but when a message is sent to inform the crew of this decision, no reply is sent. The reason is simple: the comms system aboard the boat has been deliberately taken down. Presumably, whoever did this is the Russian agent, but it begs the question: did they know that the boat was about to be recalled?

It can't have been a coincidence that comms went down just when they were most needed, does this suggest that perhaps the traitor had actually already received a tip-off? And if so, how? And from whom?

How did the Americans know about the traitor?

We do at least appear to have an answer as to why the Americans have been tracking Vigil: they were themselves aware of the Russian agent on board the boat. The question, though, is how they knew. Apparently, they didn't want to reveal the information to MI5 or the Navy for fear of risking their source. Could that source have been Burke?

Where does the incident at Port Havers fit into this?

Much of last week's episode revolved around the discovery of a cover-up relating to two accidental deaths during a previous stop at Port Havers in Florida, but this particular storyline more or less faded into the background this week. The question is, how is that event related to the news of a Russian agent?

Why was MI5 monitoring the peace camp?

After she was dramatically followed by MI5 at the end of last week, episode four saw Kirsten Longacre sit down with the intelligence services. At one point during the exchange, she asked them if they had been monitoring the camp and they admitted they were – although they insisted there was nothing sinister about this.

But before they could answer her question about why they had an operative inside the camp, the interview ws brought to a close. So the question is, was this really just routine monitoring, or is there something more going on?

What happened with Amy and Kirsten?

Another interesting thing about this episode is that it included a lot of flashbacks, all relating to Amy and Kirsten's prior relationship. We learned how they met, and how they got together – and got a brief glimpse at the beginning of their eventual break-up. Presumably, the breakdown of their relationship is going to have some sort of significance later on – but why?

Who killed Craig Burke and Jade Antoniak?

The overarching question remains – although it looks like we now have a solid answer to at least Jade's murderer. Peter Ingles, the man who turns out to be a Russian agent, is clearly the man who had raided Kirsten's house and seems very likely to also be the person responsible for Jade's death – although he is able to get away with it on grounds of diplomatic immunity.

As for Craig, we can presumably infer that whoever killed him was the Russian agent – unless that this is just a red herring. Perhaps Burke was actually killed over a more petty grievance, and his death just happened to allow the police to learn about his existence as the Russian agent.

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MI5 themselves say that it wouldn't make sense for the Russians to kill Burke given that his whistleblowing activities about Vigil not being fit for purpose would suit their needs – unless, of course, he really was aware of the Russian's identity.

It's also interesting that we've not seen any more of Craig Burke's video messages this week – let's hope we get some answers next week.

Vigil continues on BBC One on Sunday 19th September at 9pm. If you’re looking for more to watch, check out our TV Guide or visit our Drama hub for the latest news.