“It’s not something I’ll ever forget,” replied Keller. “It’s on the Castleblayney Road. A portion of his land runs along the border. During the war it was a major smuggling route between the South Armagh Brigade and IRA elements in the Republic.”

“And the shed?”

“It’s situated at the edge of a large pasture, surrounded by stone walls and watchdogs. If the PSNI goes anywhere near that farm, Fagan and Quinn will know about it.”

“You’re assuming Madeline’s there.”

Keller said nothing.

“What if Conway was lying again? Or what if Quinn has already moved her?”

“He hasn’t.”

“How can you be sure?”

“Because it’s Quinn’s way. The question is,” said Keller, “do we tell our friends at Vauxhall Cross and Thames House what we know?”

Gabriel glanced at the MI6 mobile and said, “Maybe we just did.”

They passed beneath a nest of CCTV cameras keeping watch on the M22. Keller removed a cigarette from his packet and twirled it unlit between his fingertips.

“There’s no way we can set foot in South Armagh without someone spotting us.”

“So we’ll go through the back door.”

“We have no night-vision capability or sound suppressors.”

“Or radios,” added Gabriel.

“How much ammunition do you have?”

“One full magazine and one spare.”

“I’m down a round,” said Keller.

“Pity.”

Keller’s MI6 phone vibrated a second time.

“What does he want?” asked Gabriel.

“He’s wondering where we’re going.”

“I guess they’re not listening after all.”

“What shall I tell him?”

“He’s your boss, not mine.”

Keller keyed in a message and returned the phone to the console.

“What did you say?”

“That we’re developing a piece of potentially vital intelligence.”

“You’re going to make a good MI6 officer, Christopher.”

“MI6 officers don’t operate in South Armagh without backup.” Keller paused, then added, “And neither does a man who’s about to be the chief of Israeli intelligence, not to mention a father of two.”

The motorway dwindled into a two-lane highway. It was half past two in the afternoon. Sunset was just ninety minutes away. Keller lit the cigarette and watched as Gabriel reflexively lowered his window to vent the smoke.

“You know,” said Keller, “none of this would have happened if you’d told Graham Seymour to take a hike when he came to see you in Rome. You’d be working on your Caravaggio, and I’d be drinking a glass of wine on my terrace in Corsica.”

“Any other pearls of wisdom, Christopher?”

“Just a question.”

“What’s that?”

“Who is Tariq al-Hourani?”