Her next stop was the neuro-cellular lab. If the mood about the place as a whole was gloomy, then the atmosphere where the victims had worked was wretched. Two technicians packed belongings into boxes, and both had to stop occasionally to blow their noses. A few uniforms were working on computers; Kelly recognised two young detectives from Matt’s team.

‘Hi, guys, any luck?’

They shook their heads. ‘We’ve had five different scientists helping us translate all of this stuff into English. Apart from experiments, tables and results, it’s just time sheets, shift patterns and pay grades.

‘All as it should be then?’

‘Yes, guv.’

‘So what exactly were they working on?’

‘Mood disorders.’

‘Mental illness?’

One of the technicians looked up. ‘No, I’m sorry, I need to explain.’ Kelly got the impression that the detectives had already had the lecture that she was about to become privy to. ‘Mental illness is like a long-term acute mis-wiring, but mood swings are short-term chronic episodes. For example, depression isn’t a mental illness, it’s a mood disorder. Being drunk isn’t a mental illness, but intoxication makes one act like a lunatic.’

Kelly nodded. ‘Carry on.’

‘George’s team was working on neurotransmitters, and the chemicals that switch them on and off.’

‘I’m sorry, you’ve lost me.’

‘It’s probably best if I show you the diagram I drew for your colleagues.’

The two detectives looked at Kelly and signalled their approval; it had clearly helped them, so she decided to give it a go. The diagram looked like a sketch of a broken rope. The technician explained that since every event in the body was electrical, pulses needed to jump the gaps in nerve endings known as synapses. He pointed to the broken rope and Kelly tried to imagine the size of a nerve.

‘Hold out your hand.’

She did so.

‘If I was to hold a naked flame underneath your hand, you’d feel pain, but quicker than that, you’d have an overwhelming instinct to pull away. That’s an electrical message. The same is true for feelings: they’re just messages travelling around the body, acting upon what we know and have learned already. So toddlers know very little and act in predictable ways. Adults are trickier because we’ve probably been hurt in love, we know what it’s like to make a prat of ourselves drunk, and we also know that happiness might be round the next corner even though today is awful. So we use past experience to make decisions.’

All three detectives were mesmerised by the technician and nodded along like puppies.

‘George’s team was working on how we can make those electrical connections less or more intense, depending on the need.’

‘I think I get it. Do you mean like antidepressants?’ Kelly asked.