Jack instinctively believed Charlotte’s story, and although this line of questioning had come to an unexpectedly abrupt dead end, it did serve to tell Jack what Charlotte looked and sounded like when she was telling the truth, so it wasn’t time wasted. Now he’d be able to recognise a lie when she told one.

Jack moved on to the subject of Maisie Fullworth, watching her carefully to see if she shifted from being confident to being frightened. ‘We now know that the person who broke into Maisie Fullworth’s house was not necessarily a member of this gang of burglars, nor were they necessarily male.’

And there it was! Charlotte’s face drained of blood and Jack imagined that her skin was now clammy to the touch. She swallowed noisily and looked down at the cold cup of tea in her hand.

‘This person,’ Jack continued, ‘whoever they were, was frightened away by a teenage girl. That’s the action of someone who is capable of empathy, it’s not the action of a heartless killer.’ Charlotte’s eyes flicked to Jack’s face, then down again, then to Bevan, then the mirror. She didn’t know where to look as the word ‘killer’ echoed round the room. She was clearly desperate to ask who had been killed, wondering frantically if she was responsible. As she struggled with the impossible task of hiding her feelings, the blood raced back to her face and she flushed bright red.

‘Do you know Jacob Mulhern, Charlotte?’

Charlotte’s eyes stopped on a small scratch on the desk where the laminate had chipped and she seemed to become transfixed by this tiny flaw. Jack’s voice continued, slow and deliberate. ‘He owns a livery stable in Oxford, and he ordered a plant from you recently. Do you remember delivering that to him? It doesn’t matter if you can’t. We are just trying to find the last person who might have seen him alive.’

It was at this point that Charlotte actually seemed to stop breathing.

Her wide eyes, full of tears, looked imploringly at Jack, and he reached out and wrapped her trembling hands in his own. ‘I know your role up until this point, Charlotte, but I also know what’s coming. So, I need your help. Today.’ The tears finally rolled down her cheeks. As they did, it was as though she became free, and she started to breathe again.

As Jack entered the observation room, Mason couldn’t hide his admiration. ‘Nice interview. She’s gagging to tell you everything she knows.’

Jack didn’t smile. ‘She’s not a criminal, Colin. She’s just got herself into something that she can’t get out of. I’ve now given her that way out, so she was bound to jump at it.’