"I wasn't ready to give up on you."
So, Suzie and Owen each shot Jack and then died and were resurrected. And each of their resurrections came with a price. The first time, Suzie is the one who arranged for her own resurrection and the price was Gwen's life (and Jack refused to let that happen). In this case, Jack brought Owen back and the price tag ended up being twelve people's lives.
I love Jack's vibe with Owen -- like with Tosh, it's a relationship that doesn't feel sexual, instead, it feels fraternal. Jack's the big brother to Owen and Tosh as younger sibs. He sees that Tosh is special and encourages her to shine; he sees that Owen can be saved and wants to do that (while still wanting to smack him upside the head sometimes -- what he did with Owen in the prison/holding cell was so incredibly big-brotherly). I love that Jack so clearly loves all the members of his team, but in very distinct ways -- he doesn't love Owen the same way he loves Gwen and he doesn't love Ianto the same way he loves Tosh; but he does love them all (and the way he feels about the Doctor and Rose is a completely different story, but still one about love).
Sadly for her character, I'm not sure that Martha did... anything at all in this episode apart from have the life sucked out of her and fail to get the chance to do an autopsy. On the plus side, that meant that the focus was firmly on Owen, who is a regular on the show and who did just get shot to death, so I can't be all that upset. Also, "Reset" was pretty Martha-focused, so I don't feel like they brought her on for no good reason (and we don't know what she may be doing in the next episode).
Random speculation: little girl that Jack meets with in the beginning is, in fact, the Faith mentioned in the story about death. Which means that Jack may have just made Owen immortal. The Doctor would totally verbally smack him for that. I'm amused that Owen's resurrection is like what happens if you die after you become immortal in Death Becomes Her -- bits are fragile and blood doesn't circulate. Healing is for the living.
Fantastic episode -- great acting from Burn and the others. Another stellar episode for S2.