Had she been too harsh? Too aggressive? Since leaving the pub, Charlie had been replaying her conversation with Helen, wondering if she’d pushed back too firmly on her request for help, even though she’d tried her best to be polite in doing so.

It felt odd to be gainsaying Helen, stranger still to be the one with the power, telling her former mentor what could and could not be done.

She had been right to refuse, she felt sure of that, as there was no question of her deploying police resources on a half-baked quest for justice.

Charlie couldn’t get the sign-off for it, even if she wanted to, and if she was honest, she wasn’t sure she did .

Though she hesitated to say it to her old friend, a strong sense of resentment, of disappointment, lingered following Helen’s decision to quit.

In the days after her rash resignation, Charlie had worked tirelessly to try to persuade her old friend to stay in post, but her words had cut no ice, a failure which still rankled.

Wrenching her thoughts back to the present, Charlie chided herself for allowing Helen to distract her from the matter in hand.

Today’s operation had been an embarrassing failure and Charlie was sure the reckoning would be swift.

She wanted to have something to show for their efforts before the inevitable showdown with Chief Superintendent Rebecca Holmes.

‘Right, everyone present?’ she asked, casting around the incident room.

On cue, the final stragglers joined the rest of the team at DC Roberts’ desk.

‘Then let’s begin. DC Roberts, would you mind playing the audio recording of the Border Force tip-off?’

The young officer responded, clicking the ‘Play’ symbol on his screen. Immediately the audio file sprang to life, filling the incident room with a jarring, mechanical noise. Then, seconds later, a male voice cut through:

‘Got a shipment incoming,’ the man growled breathlessly, fighting to be heard above the background noise.

‘Human cargo, twelve bodies. Arriving on the 17th on the 7.15 a.m. boat from Rotterdam. The driver’s name is Luc Peeters and he’s driving a Belgian truck, registration plate 1 AYB 209.

The end location is the Maslen industrial estate in South Portswood. ’

Then the line went dead, the audio file coming to an abrupt end.

‘Again, please,’ Charlie requested.

DC Roberts obliged, the team standing in silence as they listened intently to the anonymous tip-off. As it came to an end, it was DC Shona Williams who spoke first:

‘It’s a young male, definitely local I’d say, maybe late twenties, early thirties.’

Several of the team nodded in agreement.

‘Sounds to me like a working man,’ DC Williams continued. ‘Maybe he works on the dockside, or for one of the suppliers who cater to the workforce there.’

‘Could just as easily be a rival gang member, someone who thought they were putting one over the competition.’

‘Not very effectively,’ DC Malik offered, though her joke raised few smiles.

‘Or it could just as easily be a hoax,’ DC Roberts piped up. ‘You get all sorts of weirdos calling these hotlines, for a laugh, for attention …’

‘Or it could be some rando who’s pissed off with Adam Peeters,’ DC Williams offered.

Charlie felt a spike of anger and frustration. Peeters was the last person she wanted to think about, the aggrieved haulier having already filed an official complaint over his arrest, promising to sue Hampshire Police for loss of earnings.

‘Let’s try to stay positive,’ she insisted.

‘Let’s assume this guy knew what he was doing, that he has some knowledge of the trafficking trade, even if his role was only to muddy the waters or mislead us.

If that’s so, then it would obviously be good to locate him.

What do we think that sound in the background is? Can we place him anywhere specific?’

Roberts hit ‘Play’ once more, Charlie leaning in closer, but still she couldn’t make out what the insistent sound was.

‘Is that music? Or machinery?’ she queried.

‘Or some mode of transport? A train rumbling by …’ DC Malik responded.

‘It sounds to me like a printer of some kind,’ DC Rayson pitched in. ‘The way there’s two bursts of noise, then a brief pause, then the two bursts again …’

They listened again, everyone crowding in this time.

‘Certainly could be a printer,’ DC Williams said, although she didn’t sound convinced.

‘But surely it wouldn’t be that loud, unless it’s printing advertising posters or something?’

Charlie could feel the energy in the room dropping, so stepped in quickly.

‘Let’s not get distracted going down rabbit holes. We’ll mull on it tonight, have another listen tomorrow. What about the number the call was made from?’

‘A mobile number via a Lenovo pay-as-you-go SIM,’ DC Roberts answered, showing Charlie the digits.

‘So it wasn’t withheld?’ she responded, surprised.

‘No, it wasn’t, but according to Lenovo, this was one of only two calls that’s been made from that number, despite the fact that the SIM was bought months ago.’

‘By whom?’

‘A Mr John Smith,’ DC Roberts replied, pulling a face. ‘Given that the SIM was sent to an Amazon locker for collection and the home address given doesn’t actually exist, I think we can assume it’s not his real name.’

‘So he’s obviously taking great pains to protect himself, which would suggest there is some method here. That he’s not a random hoaxer,’ Charlie countered, seizing on this new information.

‘Even so, unless he uses the phone again, we’ve got no way of finding him. Odds on the SIM’s already in the bin.’

Charlie tried not to let her anger show, though she wasn’t entirely sure she succeeded. Was it her imagination or did the team want this operation to fail? Swallowing down her frustration, she responded curtly:

‘Maybe, but if we feel this guy is relevant, then we have to pursue him. It’s possible this man may have rung in with other tip-offs, even if he used a different number to conceal his identity.

Thanks to Border Force, we now have voice recordings of all the tip-offs made to the hotline, so our first task is to go through these, see if the same guy crops up again.

If we can get dates, times, perhaps divine a pattern of some sort, then we may be able to find him. ’

DC Roberts was looking at her with ill-concealed alarm, the idea of doggedly listening to a mountain of audio messages clearly horrifying him.

‘There are scores of them,’ he protested.

‘Then you’d best make a start straight away. Who wants to assist DC Roberts?’

There was a long pause, before DC Williams reluctantly raised her hand, followed shortly afterwards by DC Malik.

‘Excellent, quick as you can, please …’

Turning, Charlie marched off to her office, feeling several sets of eyes following her.

She could feel the mood in the room, sense their disquiet, and though she longed to tear a strip off them for their lack of belief, she understood their hesitation.

Yes, they had a lead, a slim avenue of investigation to keep them busy, but would it actually yield anything?

Or were they simply clutching at straws?