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December 1943, Union Station, Washington, D.C.

Klaus Fuchs steps off the train and onto the platform.

With him are the other atomic scientists sent from Britain to work on America's Manhattan Project.

The UK is ahead of the US in working out how to enrich uranium for use in an atom bomb.

But in order to get the bomb built quicker, Britain's agreed to loan its atomic scientists to America.

They arrived in the US this morning after more than two weeks at sea.

Now they're being taken to a security briefing with the head of the Manhattan Project, General Leslie Groves.

As the group walks through the streets of D.C., Fuchs is amazed to see a pyramid of oranges on display in the store window.

After years of wartime rationing in Britain, the abundance of food is almost shocking.

Fuchs's friend and boss, Rudolf Peels, smiles.

The war seems far away here, doesn't it?

I can't remember the last time I saw fresh oranges.

There is no rationing here?

No.

They're also going to pay us better, too. The group's escort leads Fuchs and the other scientists into a vast government building. They head down the long corridors

until they reach an airy conference room. The door opens and General Grove strides to the wooden lectern at the front.

He's a large man, but his girth is rigidly buttoned and belted into his military uniform.

Good afternoon, gentlemen.

While Dr Robert Oppenheimer leaves the science on this project,

it is my responsibility to make sure we build this bomb before Hitler does.

And that's why security is my number one priority.

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