With no one else within sight, Dempsey drew his pistol from its holster and pointed it at the agent.

‘So how do you see this playing out?’ Dempsey asked, hiding his own hesitation. The Glock 19 was trained precisely on Grace’s forehead.

‘I was hoping you’d help with that part,’ Grace replied. She eyed the pistol with concern and for the first time she seem less than certain. ‘My plan ended with that warning.’

Dempsey took one final step back. Into the shadow thrown by the elevator bank, where he was no longer visible from anywhere outside the building.

He glanced at the corridor to his left. It led to the service entrance, just past the post room. A solid metal security door, it was the only other way into the building from the street.

It was closed. And therefore locked. One followed the other.

This meant that only one open access point was available to Grace’s team. The main one.

That fact allowed him time to focus on Grace.

‘And why the hell would you give me a warning?’

‘Because I’m a Special Agent of the United States Secret Service. It’s my job to protect this country and its president. But I draw the line at murder, Mr Dempsey. I’m not an assassin.’

She sounded sincere. There was nothing in her body language to say otherwise. But in these circumstances, that was not nearly enough.

‘So what? You’re walking away from your team on principle? To save some guy you don’t even know.’

‘They’re not my team,’ Grace replied. She sounded as if she found the suggestion distasteful. ‘I live by a code. A code taught to me my whole life. I do my duty and I do what’s right. Killing you? That’s neither.’

In a career that spanned more than two decades, Dempsey had spent literally years undercover. He knew how to tell a lie. And he knew how to spot one. Skills that had kept him alive as often as his ability to kill.

Grace did not seem to be lying. Which made her either an ally or a better covert agent than him.

‘Who sent you here?’ he asked.

‘Assistant Director Jack Meyer,’ Grace replied. She spoke without hesitation ‘Head of the Presidential Protective Division.’

‘I know who he is. Why’d he send you?’

‘Like I said. He sent me here to kill you.’

‘I get that. Why?’

‘I didn’t get an explanation. Just an order.’

‘Why you?’

For the first time, Grace hesitated. When she spoke again, it was with an answer that did not justify the stumble.

‘I . . . I don’t know that. Like I said, I didn’t get an explanation.’

Dempsey did not like the answer. It was an obvious lie. But that, in turn, made everything else she had said truthful; Grace could not be such a poor liar on one subject while being an accomplished one on everything else.

It was a helpful discovery. Now that he could trust most of what she had said, Dempsey could see where Grace’s story married up with what he already knew.