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The Iron Vault: Meet Eli Mercer and Rosalie Tanaka

October 7, 2026
S.F. Baumgartner

By S.F. Baumgartner

Eli Mercer needs the archive to survive. Rosalie Tanaka needs to know what its contents can actually prove. With a destruction order already in play, neither has the luxury of taking their time.

The Iron Vault by S.F. Baumgartner displayed on a phone beside tea, autumn leaves, and warm string lights

The Iron Vault, Book 3 of The Mercer Files, releases October 20. This investigation takes us to the Pacific Northwest, where the remaining Blackwater evidence is at risk of disappearing.

Eli is a naval-intelligence systems investigator with a family stake in the case. Rosalie is a forensic financial investigator who can follow a money trail without mistaking a plausible explanation for proof. Getting access to the records is only the beginning. They also have to establish what those records mean and preserve evidence that can withstand scrutiny.

Their search moves from Bremerton across Puget Sound to a shipyard, with legal obstruction giving way to sabotage, fire, and rising water. An archive may sound like a quiet destination. This one leaves them very little room for error.

I also want to say thank you to the readers who have shared early feedback. I’ve taken it seriously while working to strengthen The Iron Vault: clarifying the financial trail, trimming repeated explanations, and making the action easier to follow. Those are the improvements I’ve aimed for, and I appreciate knowing where readers need more clarity or forward movement.

For Eli and Rosalie, the practical details have consequences. A document that cannot be authenticated may leave an accusation unanswered. Time spent checking a record is time someone else can use to destroy the next one.

This is a clean action-adventure thriller with procedural suspense and a restrained romantic thread. It closes the trilogy and can also be read as a standalone case.

Read more about The Iron Vault or preorder your copy for October 20. I’m looking forward to sharing Eli and Rosalie’s investigation with you.

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