Get ready, because there's more twists and turns in this episode than in a bowl of spaghetti.
The episode begins with Challenger and Finn mapping out the plateau. During a conversation about Veronica, Finn says, 'we're both survivors, living in a place where resources are minimal, one of us is going to have to kill the other,' Challenger- 'what!?'.. Finn- 'don't any of you have a sense of humor?'

Challenger breaks off from Finn for a while and heads off on his own little trek, during which he comes across a crashed Royal Airforce airplane. He finds a grave for one of the pilots, and deduces if one pilot is buried, another must be alive, at that moment the other pilot jumps out behind him, and knocks him out.

While Challenger lays unconscious, Finn is back at their mapping point, waiting for him to return, after getting tired of waiting, she heads off to find him.

Challenger finally wakes up to a madman accusing him of 'looking for him.' The pilot reveals that the plane crashed five years ago, his name is Drummond, and he thinks Challenger is an MI5 agent tracking him for the stolen iridium on the plane. Challenger seems to recognize the situation, and we see a flashback of Challenger being led to an interrogation room back in London.
Challenger is told that the iridium he needed for his experiment has been stolen, and he is a suspect. He makes a believable speech that he had nothing to do with it, why would he steal something that would have helped him end the war altogether, and leaves.

Back at the treehouse Marguerite gets a bit touchy when Roxton asks her about her childhood. After a pointless discussion about how they might have once met when they were children (neither one recalls the other) Marguerite makes it clear she wants the subject dropped, and Roxton sulks away to hunt, Marguerite begins to say 'I'm sorry,' but doesn't get it out.

Out in the jungle while searching for Challenger, Finn comes across a figure clothed in fur of some sort, and pursues it. When she catches up to it, we see that it's Veronica, however Finn not knowing who she is, draws her weapon on her. Veronica swings around, knocks Finn's weapon out of her hand, and gets her in a headlock, but when Finn says 'Veronica, let go, I'm your new housemate,' Veronica releases her.

At Drummonds plane, Challenger asks Drummond why he never attempted to leave, at which point Drummond explains his orders were to never leave the iridium unguarded. Challenger says he's certain that Drummonds orders would no longer be in force after all this time, but Drummond insists that if that were so, he would have received new orders, and motions to a radio nearby. Challenger inspects it and finds out it hasn't worked since the crash, but claims he could fix it back at the treehouse, and the two head for it.

Already at the treehouse, Marguerite is practicing apologizing to Roxton, when Challenger comes in with Drummond holding a gun to his back, when Marguerite eyes the iridium and comments on it, Challenger asks her how she knows about it, it's now time for another flashback.

In this flashback she's known as Baroness Von Helfing, and she's in the same interrogation chamber as Challenger was. The investigators chit chat with her first, during which one of the investigators says his job is the same as hers, to which Marguerite replies 'oh I see, you also marry rich older men, secretly poison them, and inherit their estates?' Investigator- 'why, is that what you do?' Marguerite - 'people will gossip.' After a few more shots at one another Marguerite claims that if they don't let her go, they'll have to explain it to her husband. At which point she gets up to leave, one of the investigators asks her if she's ever heard of iridium, Marguerite claims she doesn't, and denies stealing the iridium.
After she leaves, one of the investigators asks the other if she really kills her husbands, and the other says 'just be glad you're not her latest one, in Vienna, they call her the Black Widow.' We see a shadow of someone standing behind a one way mirror leading into the interrogation room, and then the flashback is over.

Challenger says they must have been interviewed between minutes of one another, and asks Marguerite if she ever found out who stole the iridium, Marguerite says she did, Drummond hearing this says she knows too much, and secrecy must be maintained, he then aims his rifle at her.

Challenger jumps up and grabs the gun saying that if Drummond expects him to fix the radio he'll leave Marguerite alone, Drummond knocks him down and claims Marguerite was about to say his leaders name. Marguerite says she never knew his name, just that he was an MI5 officer who was a double agent, he stole the iridium, and his codename was Parsifal. Marguerite then says that he was sent to prison for life. Drummond demands to know who's side she's on, Marguerite asks him if he's still going to shoot her, he replies no, and she then says 'then I'm on your side.'

Finn and Veronica are making their way around looking for Challenger while having a conversation about her parents. Finn asks her if she ever found the tribe that made the mask with the Trion (symbol) on it that belonged to her mother (mentioned in a previous episode). Veronica says she did, but it was completely deserted except for a blind Shaman that knew her name, who gave her a pendent, said her mother had worn it, and now it was her turn to know, and that was it.

Meanwhile Roxton isn't having much luck hunting, and heads back for the treehouse.

Finn and Veronica come across the airplane and follow the tracks Drummond and Challenger made to Drummonds cave where he lived.

At the treehouse Challenger is setting up the radio antennae, but suggests to Drummond that they wait until the coming storm is over, Drummond suggest that he work faster before the storm comes.

On his way back to the treehouse, Roxton is practicing apologizing to Marguerite.

Finn and Veronica are investigating Drummonds dwelling, and come across a radio handbook, they deduce that there must have been a radio to go with it, and that Challenger probably persuaded Drummond to take it back to the treehouse so he could fix it.

Roxton makes it back to the treehouse, and finds Drummond, Challenger and Marguerite explain the situation to him, and Roxton also seems to know about the whole situation! When Challenger and Marguerite ask him if he knows about it, Roxton replies he should know, he was arrested for it's theft, Drummond figures out he's Parsifal, and stands attention to Roxton...his leader.

Challenger and Marguerite can't seem to believe that Roxton was a spy, while Roxton figures out who Marguerite is.. the Black Widow of Vienna....flashback time!
In this flashback we see the two investigators who had been interrogating Marguerite and Challenger, they have concluded that Marguerite had nothing to do with it and begin to think about something a reporter named 'Malone!' told them, they believe he knew a little too much, and was informed by whoever made the theft, they then believe that the person who made the theft was a traitor in MI5, more specifically the shadow behind the one way mirror. They ask him to come in the room for a moment, when the man enters, it's Roxton donning a mustache. The two investigators begin to accuse him of the theft, Roxton never denies the accusations, but only makes arrogant threats towards the investigators, they then conclude that he did do it, and have him arrested...flashback over.

'If that's what really happened, then there's something you're not telling us,' Challenger says, Marguerite adds, 'i know you're not a traitor John.' 'You're not the only one with secrets Marguerite,' Roxton replies. He heads over to Drummond, and tells him he'll take it from here, Drummond begins to hand over his pistol, but then he says 'but....Parsifal was sent to prison for life?' Roxton replies that the British couldn't stand to send one of their own to jail and it was easy enough to make a deal. This infuriates Drumond who claims Roxton gave away his secrets to save himself while Drummond was rotting in the jungle!

Drummond grabs a pistol, Roxton grabs Drummonds hand and pushes it upward, a round fires off into the sky, which alerts Veronica and Finn who are outside the treehouse making their way to it. Drummond grabs another pistol and aims it at Roxtons stomach, and knocks him down. Drummond screams for Challenger to get back to work and then turns his attention back to Roxton. 'In this jungle I stayed true to the cause, but he put himself first, and betrayed both sides,' Drummond screams. 'Stop it,' Marguerite yells, 'Roxton betrayed no one..... I was Parsifal.'

Flashback again, this time one of the investigators says 'you're safe now,' and Marguerite comes out from one of the other rooms. The investigator explains he led his partner to believe it was Roxton who stole the iridium, and that the iridium is on it's way to their friends in South America....flashback over.

Drummond exclaims, 'you, a woman, the greatest double agent in history!?'
'No, she was a triple agent,' Roxton blurts out, 'I was the armies senior liaison down at MI5, and not even I knew Parsifal was a woman.'
Drummond-- 'Parsfial Ran the entire spy ring operating in England.'
Roxton-- 'Yeah, which meant that every and any spy in the country gave their secrets to a British woman, who they thought was working for the enemy, but she was really working for England, working to keep those secrets safe.'
Drummond-- 'But Parsifal planned the theft of the iridium!'
Marguerite-- 'We needed to give him [Roxton] a success that would convince Berlin he was effective, without jeopardizing the war effort.'
Challenger-- 'what! my work could have ended the war effort.'
Roxton-- 'I'm sorry George, but as a volunteer who was arrested to protect Parsifal, I chose your work as the sacrificial lamb.
Challenger-- 'In heavens name why?'
Roxton-- 'Because of the Summerlee Commission, he headed a secret committee that revealed special ongoing defense projects, they judged the likelihood of their success.'
Challenger-- 'And he thought my project unlikely to succeed?'
Roxton-- 'Not in time for the war, look for what it's worth, I've regretted my decision every since.'
Drummond ends the bouncing ball of revealed secrets with an outburst of 'you're all lying,' and demands that the radio be fixed now!

Challenger says that they need to dissconnect the antennae because the storm is so close.
Just then the elevator begins to rise and a figure standing in Veronica's fur jacket appears, Drummond runs towards it and fires at it, just as he notices there's no one wearing the coat Veronica and Finn jump in through the window. Veronica throws her knife at him, and Finn fires her crossbow, still unstopped, Drummond picks up the radio to throw at them, but wouldn't you know it, lightening strikes the antennae just as he's holding the radio, and down goes Drummond.

After everyone has collected their thoughts and straightened things out Roxton and Marguerite engage in a conversation about the coincidence of them all being involved in the same situation before they even met. Marguerite says, 'you don't suppose it's possible that....well we're not all here by accident,' Challenger barges in and dismisses it all as random 'happenstance.'

Veronica and Finn then walk in chuckling to one another. Marguerite notices Veronica's pendent and comments on it, Challenger says it's the same symbol that was on Summerlees mask, and furthermore, it's made of iridium!

Roxton says, 'well George if you can believe that all the mysteries of the plateau might have one answer, why can't we believe we've all been brought here for a specific purpose?' Challenger takes the final comment of the episode with, 'whatever could that be?'