The hotel and shopping center had security guards. The doormen of apartment buildings kept watch even on Sundays, which they spent in vertical trances listening to soccer games on earphones. But no one had seen anything on a recent night when a gang robbed the ritzy Italian restaurant next to the shopping center. The robbers were fit, efficient, their hair close-cropped; they barked commands as they relieved diners of valuables. The word on the street: the stickup artists were off-duty cops from the Bonaerense, the police force that patrolled the province of Buenos Aires, an expanse the size of France surrounding the capital. A wave of robberies downtown was part of an ancestral feud between the provincial police and the federal police, who patrolled the city.

The federal beat cop strode to the curb, his cap at a low jaunty angle. He and the motor cops exchanged greetings and kisses on the cheek. Pescatore made his way around them. He was an armed U.S. civilian on foreign soil. Despite the investigator credentials that Facundo had provided for him, despite the rule-breaking he saw at every turn, carrying a gun made him a bit nervous. And he wasn't comfortable with all the kissing. Argentine men kissed each other with alarming frequency. It wasn't some sissified European thing confined to actors and fashion designers. Kissing was a common form of greeting among waiters, garbagemen, bank tellers, soccer players, airport baggage handlers, and, yes, cops.

The hotel had marble columns, plush rugs, and a musty air. Pescatore went up to the suite of the American client. Dr. Block greeted him wearing a suit and tie. They sat in armchairs. Pescatore leaned forward with his elbows on his thighs, fingers interwoven. This was the most delicate assignment that Facundo had given him.

"You doing okay, Dr. Block? Jet-lagged? Want some coffee?"

"I'm fine, Mr. Pescatore," Block responded in a weary monotone. "Just anxious to get this thing done with and go home."

"Please, Doctor, call me Valentine."

Block was a pediatrician from Miami. He had a shiny bald head, a white mustache, a gentleness that came from decades treating little kids. But his blue eyes behind his glasses seemed drained of light. He was the saddest man Pescatore had met in a long time. Block's son had been an engineer married to a Brazilian woman. A public-works project took him to the Triple Border region where Brazil, Paraguay and Argentina meet. He got into a dispute with an Argentine investment partner: a lawsuit, allegations of embezzlement, death threats. During a visit to Paraguay, the younger Block was shot dead at the wheel in a car-to-car ambush.

The Paraguayans hadn't done much of anything about it. Dr. Block hired Facundo, who ran a private investigation agency operating in the tri-border area and Buenos Aires. Facundo helped the FBI identify a hit man and track him to Buenos Aires, where the Argentine police arrested him. The evidence pointed at the former business partner as the shot-caller, but the investigation had stalled. Facundo had warned the U.S. embassy that the killer was likely to be released. Official options had been exhausted.

As Facundo's operative in the capital, Pescatore had been instructed to carry out the unofficial option.

"Doctor, this is the situation," he said. "Bottom line: The judge is gonna cut this guy loose. Unless he gets paid. The figure they named is forty thousand dollars. We recommend paying. It should keep the suspect in jail and get the investigation moving again."

The doctor stared with his defeated eyes. "If I may ask: How did they arrive at that particular price?"

"We think he got thirty thousand from the other side."

"An auction."

"Exactly. I feel terrible about it, but that's the deal. We have an appointment with the judge this morning. If you approve."

Excerpted from The Convert's Song by Sebastian Rotella. Copyright © 2014 by Sebastian Rotella. Excerpted by permission of Mulholland. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.