In Part 4 of Twin Peaks: The Return we were left with one of the series most tantalising cliffhangers yet - just who was the mystery woman that Albert & Gordon referred to, whose insight they'd seek into the disturbing situation with Coop? The fandom that became was rife with speculation, from Audrey Horne to Sarah Palmer, but a front runner quickly emerged in the form of Diane, Coop's often referred to but as yet unseen secretary. During the first two seasons, Cooper would record his observations, on the case and sometimes life itself, into a dictaphone, addressing them always to 'Diane...'; a memorable and fondly parodied quirk, Coop's obvious affection for Diane radiated out into the fandom.
Logically Diane felt a sound assumption; she had spent years working alongside him, listening to all those tapes in which Coop would pour his thoughts and feelings, so surely she would know him better than anyone? In Part 6 we got our answer when Albert arrived at dingy lounge Max Von's and sitting at the bar was the platinum goddess herself, Diane; beautiful, glamorous but with a sense of fragility. In Part 7 Albert tells Gordon that Diane bluntly refused to get involved ("..no fucking way") and that Gordon would have to try and convince her himself. The dynamic duo then visits Diane at her home and we meet her for the first time properly; immaculately turned out and exquisitely styled, dropping F-bombs with aplomb and smoking like a trooper, Diane is like the epitome of cool confidence, but just underneath feels damaged and defensive. Initially uncooperative ("fuck you Gordon", "fuck you too, Albert"), she soon cooled by Gordon's charms and agrees to at least see Coop and give her opinion.
In a tense and unsettling encounter, Diane comes face-to-face with Mr. C at the prison in South Dakota; she appears surprised by his physical change and seems to sense something is off. She asks him if he remembers the last time they saw each other, seemingly disturbed by the memory herself, and Mr. C, chillingly vacant, replies "I'll always remember that night". Diane looks into his black eyes and questions him repeatedly, "Who are you? Who are you?", to which Mr. C blankly replies "I don't know what you mean, Diane". Having seen enough, Diane leaves in shock and fear and confirms to Gordon outside that Mr. C is not the Cooper she once knew. When Gordon questions her about what happened that night, Diane simply says "You and I, we need to have a talk sometime", and leans into Cole for comfort; Cole for his part, doesn't quite embrace her and if anything seems a little distant.
There is a sense of something deeply amiss between Diane and Mr. C. The evil analog of Coop had clearly visited her sometime after leaving Twin Peaks and whatever went on between them had a traumatising effect on Diane. Had he physically or sexually assaulted her? Suddenly Diane's abrasive attitude to the subject of Cooper, her guarded nature and her obvious trepidation in seeing him again seemed to make troubling sense. But, as so often is the case in Twin Peaks, first appearances might not be quite what they seem...
"Around the dinner table, the conversation is lively."
- Mr. C, Part 9, Twin Peaks: The Return
In Part 9 we see Mr. C, post Ray double cross, and subsequent supernatural recovery, deliver the above-coded message to someone via text; later in the episode, we're shocked to discover the recipient is his former (?) secretary Diane. When the FBI arrives in Buckhorn to examine the body of Major Briggs and head to the morgue to investigate, Diane makes a flippant excuse to stay in the waiting room and smoke; as the others leave, Cole turns and makes a questioning expression. Earlier we'd seen Diane check her phone on the FBI plane, only to have no signal; in the waiting room, she seems nervous again before a text comes through and we see it's the code Mr. C sent. Diane deliberates for a moment and then sends a reply we don't see.
Given her last interaction with him, the suggested history between them, and the genuine fear & anxiety she displayed, this turn of events between Diane and Mr. C seemed unfathomable. How did Mr. C know how to contact her; did this mean they'd been working together? And if so, under what circumstances - bribery, psychological manipulation, force? Or is she simply his willing partner, in crime and even passion? Her behaviour in subsequent episodes seems to reduce those possibilities down somewhat.
Part 10 gives the first strong hint that something very bad is up with Diane. Albert reveals to Gordon that they have intercepted the cryptic note to her and that her response advises the FBI have Hastings, and he is going to lead them to 'the site'. Gordon replies that "I felt it when she hugged me, and this confirms it". Confirms what exactly we aren't told, but the suggestion seems he feels she is playing against them. Gordon was noticeably cool during their hug, maybe sensing her emotions and therefore her motivations were not honest. The fact she is covertly communicating with Mr. C would indeed confirm a dishonesty. Perhaps Mr. C's cryptic phone call from prison - "The cow jumped over the moon"- was actually made to Diane, another piece of code to tell her how to proceed with the plan? We haven't actually learned whether Warden Murphy revealed the content of that call to Cole, but it would certainly reinforce this idea.
When they visit the aforementioned site in Part 11, Albert & Gordon tell her to wait by the car while they investigate, and they have their conversations deliberately out of her earshot. Although no clear shot of the screen is shown, Diane again spends time texting whilst they are there. Maybe it's just coincidence that a woodsman, who quite possibly acts at the behest of Mr. C/BOB, arrives to dispatch Bill Hastings not long after she is seen on her phone. Later in the episode, Albert, Gordon, and Diane are sat discussing the events, specifically the coordinates found on the corpse of Ruth Davenport; Albert holds out a photo for Gordon in such a way that Diane can also slyly see, but she doesn't notice Albert watch her memorise the numbers. At this point, it seems clear the FBI is using her line of communication to Mr. C to their advantage, but her moral allegiance is still cloudy.
An unsettling scene in Part 12 possibly makes it clearer. After enlisting Tammy officially into the Blue Rose Task force, Gordon calls Diane in to join them from the next room and she wafts in through a pair of red velvet curtains that are highly reminiscent of the Red Room. When he tells her they want to temporarily deputise her to officially assist in discovering what happened to Coop, Diane callously responds, "What's in it for me?" Albert tells her and when Gordon asks if she's in, Diane replies, "Let's Rock" and makes a 'shooting-gun' gesture with her fingers.
This is disturbing for two reasons - firstly because 'Let's Rock' is a phrase associated most with The Black Lodge; it's written in lipstick on Chet Desmond's car after his unexplained disappearance, and The Man From Another Place says it just before all hell breaks loose during Coop's nightmarish Red Room experience, which ended with Coop being replaced by his doppelganger. Secondly, when Diane says these words, they're accompanied by some Black Lodge sound effects, ones that are heard during Jeffries vision of the convenience store, featuring a dinner table around which the conversation is indeed lively. Together this all seems to suggest that Diane is probably not a coerced victim of Mr. C's manipulations, but a willing participant in his dabbling with other worldly forces.
So if Diane is working with Mr. C, what could be motivating her? It's been noted multiple times now that Diane has knowledge of the Blue Rose cases from her previous work with Coop, so perhaps she is in for the power. Dougie-Coop seem to passively radiate good fortune and well-being in those around him, drawing out their natural kindness and goodwill, sometimes from the most surprising people (The Mitchum Brothers for example); perhaps Mr. C, a being driven by pure selfish craving, by 'want', brings out and engorges the very worst impulses of others - the thrill of living outside the rules can be intoxicating indeed. Perhaps Diane just has a thing for the bad boys - the very bad boys...
Whatever has been driving Diane's actions so far, I have a feeling there's more twists and turns in her tale yet. Mark Frost & David Lynch have positively revelled in playing with and outright subverting our impressions of characters, and we've still a third of the way to; Laura Dern's fabulous performance means I'll be entertained and riveted no matter what. And however her eventual fate turns out, I've no doubt Diane will go down as one of Twin Peaks most memorable and exciting players.