His eyes ballooned in their sockets and he staggered backwards, allowing Rosa to withdraw the knife and stab him in the chest. It sent him sprawling over the wall and onto a patch of grass where his body convulsed in a death shudder.

She then threw the knife onto the ground next to him and took the pistol from the rucksack, which she simply discarded.

Without a moment’s hesitation she burst into the restaurant. It was about half full and there was soft music playing in the background.

Heads turned towards her as she strode across the room with her pistol arm raised. But she stayed focused on the two men at the far table next to the window.

As soon as they realised what was happening, they both jumped to their feet, which made it less likely that Rosa would miss them.

She took aim and let loose with the machine pistol. Amid screams all around her she watched as the bullets tore into her victims, spraying blood over the window and the white tablecloth between them.

Both men hit the floor like bags of cement and she shot them several more times for good measure.

Then she turned around and fired a few more rounds into the ceiling so that none of the customers or staff would be tempted to approach her.

But she needn’t have worried because those who hadn’t already dashed out of the restaurant were cowering under the tables.

Outside, she dropped the gun, mounted the bike, and with a screech of rubber she made her escape.

It was another job well done and she was pleased with herself.

Five minutes later she was back in the car, having removed the helmet and leather suit.

She told Miguel that it had gone without a hitch and that the two Los Zetas enforcers were dead.

‘Carlos will be pleased,’ he said. ‘You did well. Now I will take you back to your hotel.’

‘I’m not going back yet,’ she said. ‘I want you to drop me off at a nightclub that you know will be lively tonight. I need to wind down.’

His response to this was to laugh.

‘You are a strange one, Miss Lopez. I’ve never known anyone to want to party straight after committing murder.’

Rosa ignored him and looked out the window. She didn’t need someone to tell her that she was strange. After all, anyone who made a living killing people could not, by any stretch of the imagination, be right in the head.

But it was OK because she was happy with herself and life was good. She was never troubled by the constraints of a conscience or the burden of a moral compass. It made everything so much easier.