April 24, 2014 5:00 PM EDT

April marks the 20th anniversary of Nirvana frontman Kurt Cobain’s death, and Lucky Them, which screens at the Tribeca Film Festival this week, revolves around another departed Seattle music hero — albeit a fictional one.

Toni Collette plays Ellie Klug, a veteran rock journalist weathering a series of hopeless flings with much younger musicians, as well as the decline of print media. When Ellie’s editor gives her an ultimatum — deliver a killer story or pack your bags — she resolves to learn the truth about what happened to her ex-boyfriend Matthew Smith, the legendary songwriter who disappeared 10 years before.

Wealthy former flame Charlie (Thomas Haden Church), who decides to make a documentary about Ellie despite his hatred of rock music, tags along for the journey about self-discovery and letting go of the past. TIME caught up with Collette and Church to talk about their friendship, shooting in the Pacific Northwest and the movie’s surprise cameo.

TIME: What attracted you to the script?

Toni Collette: What each of the characters go through, the journey, the changes that they make, the humor, the tone — when there’s something that’s incredibly moving and then incredibly funny, slapping you around left and right. It’s really weird actually, I’m kind of a lazy actor. If I know that I can do it, then I want to do it. I don’t actually look at something and go, “Oh, I can’t do that, I should try and do it.” I immediately feel like, “I can do that.” Do you get that?

Thomas Haden Church: Well, I was involved in the movie for so long, whenever I would visit [the character] over the almost seven years I was attached, it was just, “Oh, there’s that guy, and some day I might be that guy in this movie.” This sort of wealthy guy who’s a philanthropist [yet] at the same time has this quirky sensibility that’s unsatisfied. When he meets Ellie again and he becomes aware of what she wants to do, he wants to attach himself in some way because of his curiosity. Finding a guy that everyone thinks is dead, the fact that she’s a rock journalist and I don’t like rock music, wanting to know why people do like rock music — we just go on this journey together. I just always thought they were intriguing characters and they really, in such an untoward way, help each other and, further into the movie, start to genuinely care about each other.

Charlie’s personality seems hard to pin down — he’s hilariously awkward, but he also seems very self-aware at the same time. Does he just not care because he’s super wealthy?

Church: Those are all very astute observations, because it was something that was discussed a lot. He is a socially awkward guy but also has this bizarre confidence that might be informed by his independent accomplishments financially. We just briefly touch on it, but his family at one point had been wealthy and lost all of their wealth and came up in that enigma. They used to be so elite, and then they lose it, and then they regain it. I think there’s going to be an inherent frailty, but the undercurrent is, “I can always take care of myself.”

Collette: I think that’s a similarity, right? Between the two characters?

Church: It’s very much a similarity. She has this outward shell of invulnerability when, in fact, she’s incredibly vulnerable and goes through all of these fleeting arrangements. It’s because she is completely unfulfilled since she was with Matthew, which makes opening that corridor so much more painful. Charlie’s there not only observing it all, but documenting it on a camera, which takes the pain to another level. When she’s going through stories of her childhood and teenage years and how awkward it was to lose her virginity, she’s telling Charlie these stories, but here’s this camera. The pain is taken to a different level of examination. Like even worse than a therapist! A therapist with a videographer.

Collette: I think it’s really common for people to feel frustrated in their lives and want to make change but either don’t know how to, or they do know how to and they’re too scared to actually do it. That’s where Ellie begins, and through this kind of very unlikely bond — friendship, ultimately — it all starts to open up.

Church: They started to need each other

Collette: They allow themselves to soften. Allowing yourself to feel vulnerable after feeling loss and pain and building all those walls for so many years, that’s basically what she does.

Ellie and Charlie spend a lot of time in the car together, and while Lucky Them isn’t exactly a hardcore road trip movie, that is a big part of the story.

Church: Oh yeah!

Collette: They dabble, and they return.

Is being trapped in an RV the secret to their partnership?

Collette: Concentrated time in a very small space together? Yeah, I think that does something to people.

Did the cast take any road trips together? Washington looks stunning.

Church: Making the movie was a road trip. We’re in the car alone, we’re in the RV sometimes alone, but yeah, the roadtrip of the movie, of making the film, of getting to know Toni. The first week, I didn’t know her at all, but the third week really felt like we were starting to enjoy each other’s company, and by the end of the movie, really enjoying the friendship and looking for Toni. Getting to to set and wanting to find Toni and make her laugh and make her smile or talk about something.

Collette: “Where’s my buddy?”

Church: Even though you don’t shoot a movie chronologically, not always, it was very much developing a friendship with somebody, and I do think it has a very similar arc to the characters.

[Note: Stop here if you don’t want to read major spoilers.]

In the movie, Ellie and Charlie set out to discover what really happened to her ex-boyfriend and musician Matthew Smith. In a small, uncredited role, he’s played by Johnny Depp. Was that twist a surprise for you as much as it is for audiences?

Church: That only came together the week before he did it. I was attached back in 2006 and even then, Emily Wachtel, the writer-producer, she always talked about how Johnny was the perfect actor to play that character.

Collette: Everyone said, “You’re dreaming.”

Church: Including me!

Collette: And me! Everyone.

I thought it was a perfect fit.

Collette: It is, ultimately.

Of all the actors out there, Johnny Depp seems particularly mythologized.

Collette: Which is why Emily wanted him to do it, because he does possess that. People project so much on him, and there he is, the real person fixing a fence.

Church: I know him a little bit and have for a long time, and he always wanted to be enigmatic, but in a meaningful way, not in an “I’m an untouchable guy living in France” way. Everyone’s like, “He lives on island!”—I see him in L.A. all the time. He wanted people to think he was removed and disconnected, and it’s perfect for Matthew. It was the perfect enigma.

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Write to Nolan Feeney at nolan.feeney@time.com.

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