In the present, both Nikki and Paulo keel over. Doing some detective work, Hurley, Sawyer and Charlie determine the couple has evidently killed one another over a diamond heist gone wrong.
In flashbacks, we see how Nikki, an actress, and Paulo, a chef, poison an elderly TV producer and steal his diamonds. They're on their way from Australia to Los Angeles with the loot when their plane crashes.
On the island, Paolo finds the luggage containing the diamonds, but doesn't tell Nikki. He fears she's just after the money and will dump him if she has it. Without the diamonds, he has a chance at a future with her.
Nikki, however, learns the truth, and flings a poison spider at Paulo. The critter, Nikki learned from the later Dr. Artz, has a bite that paralyzes its victims. In humans, the bite paralyzes for up to eight hours and a victim's heartbeat become virtually undetectable. Something Nikki forgot thought is that, once released, the female spider attracts equally poisonous males from miles around. So, moments after Paulo gets bitten she does, too.
The couple meets an ironic end, buried alive but seemingly dead by their fellow crash survivors.
Clues, observations, speculation:
* We see that Nikki and Paulo discovered the Pearl station before anyone else did, but kept the information to themselves.
* Hiding the diamonds in the bathroom of the Pearl station, Paulo overhears Ben and Juliet spying on Jack. Ben reveals how he intends to convince Jack to operate on him. This sets into motion to whole process of luring Michael to go in search of Walt and the eventual captivity of Sawyer, Kate and Jack.
* Soon after the crash, we see Ethan Rom come up to Nikki and Paulo pretending to be a fellow passenger offering them help.
* Paulo stole a walkie talkie from the Pearl and Sawyer and the rest discovered it. Will this help them eavesdrop on the Others?
* In "The Man from Tallahassee" Locke is seen watching "Exposé," the show Nikki guested on.
* Sun learns it was Charlie, not one the Others, who attempted to abduct her. The whole thing was rigged as a diversion for Sawyer to steal the guns from the Hatch.