The 39-year-old actress, who plays Ziva David on the CBS series, shared details about her character's Season 17 guest arc in an interview with Entertainment Tonight published Tuesday.
De Pablo starred as Ziva in Seasons 3-11.
Her character appeared to die in a mortar attack in Season 11, but returned in the Season 16 finale to warn Leroy Gibbs (Mark Harmon) he is in danger.
DePablo will appear in five episodes of Season 17, which premieres Tuesday.
She said she worked with writer Gina Monreal to create a "complex and riveting" reason for Ziva's return.
"We came to the conclusion that she has been in an undercover operation and that she's been working undercover to protect her family," DePablo said.
"Then whatever would make her break that operation, would have to be a legitimately important thing."
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"I said, 'Let's bring her back because Gibbs is in potential danger,' and I think it's a legitimate reason to break any kind of an operation and to justify potentially putting other people in danger," she added.
DePablo said Gibbs being in danger presents a high stakes, life or death reason for Ziva to break her cover.
"No one leaves an undercover operation for just a simple reason," the star said.
"If that's respected, then you're opening up a chapter that could potentially be compelling, complex, certainly interesting, at times entertaining, but all of it playing simultaneously."
DePablo also discussed her return during Tuesday's episode of "The Rachael Ray Show."
She said the five years Ziva has been missing play a "crucial" role in the new storyline.
"I thought coming back would be fantastic, and I thought, you know, if you're going to bring me back, just make sure that you understand that the character's been gone for five years, and that obviously, whatever she's been doing these five years are crucial," the actress said.
"If she's disappeared, if she hasn't kept in touch with anyone, if she's in an undercover mission, make that relevant to the story," she added.
"Make that be complex and mysterious, so then you can draw from that to make this a riveting story."
De Pablo previously said in 2016 that she left "NCIS" because the scripts weren't good enough for Ziva.
Season 17 premieres Tuesday at 8 p.m. ET. CBS released a trailer for the new season featuring de Pablo in August.
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