The ending should have a twist... or should it?

Sarah sank into an armchair and let out a satisfied sigh. It was good to be home. As remarkable as it seemed, the house was just as she’d left it, all those weeks ago. Or if there were differences, they were small things – a layer of dust on the furniture, a pile of unopened letters in the hallway, the gentle click of a pistol being cocked. Wait, what?

‘Get down on the floor!’ screamed the masked gunman, kicking open the kitchen door. ‘Face down! Face down!’ Sarah hesitated for a moment.

‘Freddie?’ she said. ‘Freddie, is that you?’ The gunman froze.

‘No,’ he said.

‘What are you doing?’ asked Sarah. ‘I thought we were a team.’

‘We were,’ whispered Freddie. ‘But that was before...’ He reached up to his face and gripped his mask. Sarah braced herself. ‘Before...’ He pulled aside the fabric. Sarah couldn’t look. ‘Before this,’ he said, throwing the mask to the floor. ‘Look at me, Sarah. Look at what you’ve done to me.’ She slowly raised her eyes to his. A second passed. ‘You did this, Sarah,’ he said. ‘You gave me this big smile by being so lovely.’ Sarah grinned back at him.

‘You big silly,’ she said. ‘You had me worried there.’

‘Worried? He laughed. ‘What could there possibly be to worry about? It’s all safe again. We won, Sarah.’

‘I think you mean I won,’ said Sarah, turning into a werewolf which she had been all along and eating him.