Changed my mind about callum

So i was pretty set on the idea that Callum was a future plot point - like a double agent, or some sort of shadowy person-who-is-not-what-he-seems

Also, the condom discussion, what was that? I thought, surely, 'checkhov's gun' for something or other that's yet to come

But rewatching Episode 7 of S3, I've changed my mind.

I think Callum, as a character, was there to allow a specific kind of character development for Kate. He's not a plot arc, he's a character-development arc.

He is planted in S3 to advance the Russian sub plot, of course, but as Kate's love interest:

- for her to realize that she IS part of the chaos in her marriage to Hal
- that she doesn't treat Hal fairly / respectfully at all times (Callum's pointed response to Kate that 'if we were married for 15 years, this still wouldn't be ok')
- That she does have a pattern in terms of who she falls for, and how she handles that
- And I think something particularly interesting, at the end of Episode 7, when Kate asks Callum, "are you done with me?" but where you can tell she fully expects him to say "yes, i forgive you". And she doesn't get that from Callum -- you get the sense that she WOULD get that from Hal; she sort of expects that her bond (with Hal, which is probably a fairly conditioning expectation), is such that she does expect forgiveness, even if she's caused annoyance.
- Kate also, importantly, sees things that Callum doesn't have but Hal does: Callum confronts her about self-sacrificing his career as something that Hal would do. and Kate acknowledges that. Later, when Callum expresses relief he doesn't have to burn himself (or his career) to convince Trowbridge that the Russian sub is real, you can sort of see Kate working through -- i don't know, disappointment? -- that Callum here is no Hal

So now, in light of all of this, I think, you know, maybe that's actually all that Callum was meant to do. And if you consider where Kate lands at the end of Episode 8 -- this tilting back to Hal, is, in large part, because of stuff that Callum has shed a light on passively (being "not Hal") or actively (making Kate realize she has her own repeated patterns of behavior that are out of bound)

Which is a pretty good outcome for a secondary character in terms of plot development.

Maybe that was all that Callum was supposed to do, in the end.