On a routine intelligence gathering mission in Tehran Jack Ryan, Jr has lunch with his oldest friend, Seth Gregory, an engineer overseeing a transcontinental railway project. As they part, Seth slips Jack a key, along with a perplexing message.

INSPIRATION FOR THE THRILLING AMAZON PRIME SERIES JACK RYAN . . .

Tom Clancy's Under Fire is another breakneck Jack Ryan Jr. adventure novel from one of Clancy's most successful collaborators: Grant Blackwood.

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Campus operative Jack Ryan Jr is in Tehran, when he meets an old friend, Seth.

As they part, Seth passes Jack a key, gives him a cryptic message - and vanishes.

Now MI6 and the CIA are after Jack. They're desperate to find Seth. Jack tells them he knows nothing - but perhaps he knows enough to find his friend on his own . . .

In a dangerous foreign country, chased by agents from all sides, unsure who - if anyone - he can trust, Jack has few clues and no space for mistakes.

He's risking everything for Seth. But whose side is his old friend on?

And what if it's not Jack's?