The men on the ground had made better progress than anyone expected: the helicopter made several sweeps over the whole area: the grounds of Old Pitkirtlyhill House, the towns of Torryburn, Pitkirtly and Culross, Pitkirtly and Preston Islands and the mud-flats in between them, and nobody saw them. Amaryllis couldn't believe Mal and Jimbo had just vanished into thin air. For a few moments she wished she was on the ground chasing them. If they had skied along the line of trees it would have been easier to follow on foot than from the air. But surely they would have to emerge at some point.
Listening in on a headset she heard an exchange of radio messages between people on the ground and the pilot. A place was named where the helicopter could touch down, but it hovered for a while. Just after that, the helicopter suddenly lurched, the pilot corrected it and they headed out to the middle of the river.
'Sudden cross wind,' Amaryllis shouted in Charlie's ear.
'Are you enjoying this?' he shouted back.
She nodded and smiled. 'How did you know?'
'Your hair!' he said, and pointed at her head. 'It's standing on end.'
Her hands instinctively went up to try and smooth it down, but it was a lost cause, what with the adrenalin that always seemed to go straight to her hair, and the draught that whistled through the interior of the helicopter.
Charlie's expression told its own story. He would have done anything to avoid this sort of scenario, she knew. Almost like Christopher, except that none of it seemed to have an impact on the loose partnership between him and Amaryllis, which she knew some people considered completely incongruous. It seemed to work though. The helicopter hovered over Pitkirtly Island for a few minutes, then circled above the mud-flats in the bay. It was frustrating not being able to see the action at closer range, but she had a lot of sympathy for the idea of not being caught in cross winds. She listened to the headset again and frowned.
'Still no sign of them,' she called to Charlie. Even in this raised voice he detected a note of grudging admiration. 'They've disappeared, maybe gone to ground... There's going to be hell to pay in the army over this - they always claim they can spot people who are likely to do this kind of thing, and to alert the civil authorities to people leaving the forces. But presumably you didn't get any word of it?'
'Nobody would have told me anyway,' said Charlie gloomily. He had spoken almost too quietly for her to hear, but she sensed that he hadn't really been speaking to her at all.
'Not your fault!' she yelled.
'Too bothered about the weather, and Christmas... We had Christmas dinner at the station... Microwaved sprouts. Might as well have been cold pizza... Minds on the job instead of...'
She wasn't sure if she had heard him properly. What was all that about microwaved sprouts?
'Charlie, what are you talking about?' she shouted in his ear. 'Microwaved sprouts? Cold pizza?'
'We had Christmas dinner,' he shouted back. 'At the station. Instead of concentrating on the job. Might as well have been cold pizza.'
'Everybody deserves a Christmas dinner,' she yelled, although she was far from convinced of the truth of this.
As the helicopter's circuit widened to include Preston Island and Culross, Amaryllis glanced down. The top of the old mine shaft leading to the workings that had once extended out under the Forth caught her eye. There were patches of snow scattered across the seaweed, but it was freshly fallen and would melt quickly with all the salt water and mud around it. She pictured men working in tunnels far below, in constant fear of the water breaking through and drowning them, or the tunnels collapsing and burying them forever in layers of rock and mud. She shivered. They had worked there all the year round, even in this weather. Who knew how many tunnels criss-crossed each other below the mud flats, as well as inland around the power station?
'Tunnels!' she exclaimed aloud. 'There are tunnels under Pitkirtly. That's what they've done!'
Charlie stared at her blankly.
'Tunnels!' she said again. 'There are tunnels all around here. Old mine workings. Mal and Jimbo haven't gone to ground – they've gone underground - that's why we can't see them.'
Charlie was still staring as if she had grown two extra heads. She remembered something important.
'The maps! From the kitchen table!'
She slid her hand into her pocket and brought out her mobile phone, hoping the pictures she had taken of the maps were still there. Of course they must be: she hadn't archived anything off recently: she hadn't had time. The only thing that might have gone wrong would be if Christopher had used the opportunity of staying at her flat overnight to play with the settings.
As she navigated to the image store and retrieved the maps, she knew she had been worrying unnecessarily. Christopher treated his own mobile with the caution that most people would have applied to an unexploded bomb. He wouldn't have dreamed of touching an unfamiliar phone that didn't belong to him. She peered at the maps on the small screen. She wished now that she had given in and bought reading glasses. But it didn't matter too much. All she had to do was to remember what Christopher had found in the library that day when they had looked it all up.
'It looks as if they must have gone into a tunnel before they even hit the main road,' she said, zooming in and using the touch screen to trace the probable route taken by Jimbo and Mal.
'I thought all the tunnels around here were flooded years ago,' said Charlie, looking puzzled.
Amaryllis consulted the map images again. It was all coming back to her. She could almost hear Christopher speaking, in the quiet but confident voice he used when he was talking about history and archives. Not that she encouraged him to do that under normal circumstances. She didn't want to be bored to death, after all: there were other, worthier ways to die.
After a while she spoke to the pilot. 'Can you put us down on Pitkirtly Island?' she asked.
'You're joking, aren't you?' said the pilot's voice in the headphones. 'You'll be a sitting duck if I winch you down. And there's no way I can land around there. They've set up an exclusion zone for ten miles round Longannet – that was HQ telling me more about it just now.'
She sighed, consulting the maps again. 'OK, near that little wood then. Behind Sunk Causeway.'
'We're waiting for reinforcements,' he said censoriously. 'They're arriving by boat in twenty minutes.'
'But we won't be in the way,' Amaryllis protested. 'I just want to check something out near the island.'
She had visions of making her way through the tunnels with Charlie and taking out the conspirators. Then she looked at Charlie's face. Was he up for it? He had always seemed far too sensible. Too law-abiding. Playing it by the book.
Like Christopher.
She sighed again. Why was Christopher in an ambulance when she needed him? He would have tried his best to stay completely law-abiding, but she knew from previous experience that in this kind of situation he would just follow her lead and do what she asked him to do – unless it involved keeping mobile phones charged up and switched on, of course. She wasn't sure Charlie would be so ready to relinquish responsibility to her. In fact she was almost sure he –
'When you asked if he could put us down, what did you mean?' he asked.
'I meant I want to be on the ground where the action is, not skulking up here as if I were watching the whole thing on television,' said Amaryllis.
'Yes, but 'us'?' he said.
'You can come with me if you want,' she said. 'But there are rules. You've got to forget you're a boring policeman.'
'Hmm.'
'You've got to do what it takes.'
'Oh, yes?'
'And remember, Christopher will kill you if anything happens to me.'
'That'll be right,' he muttered as the co-pilot helped Amaryllis into a harness. 'I'd better do it, I suppose. It won't be any stupider than any of the other things I've done lately.'
She smiled at him just as she slid over the edge. 'Up to you,' she said. Then the cold air hit her and she shivered all the way down to the ground. She landed well, went into a crouch, dodged behind the nearest tree and called Christopher on her mobile phone. When he didn't reply, as she had thought he wouldn't, she called Jemima instead.
She wasn't surprised when Charlie arrived on the ground a few moments after her, in the middle of the conversation. He joined her behind the tree and waited patiently while she spoke, only stamping his feet once and rubbing his gloved hands quite unobtrusively.
There was a lot of background noise and she found it hard to make out what Jemima was saying, but the gist of it seemed to be that something strange had happened when she and Dave were making their way back to Pitkirtly.
'... got them in the car... pease brose,' was what it sounded like.
'Who do you have in the car? And what's pease brose when it's at home?'
'No, we're going home,' said Jemima.
'But who's in the car with you?'
'It's Christopher, of course,' said Jemima. 'And some old man with him – I don't know who he is. He's wearing a tweed jacket. And wheezing a lot.' Her voice lowered slightly. 'He looks as if he's been living rough for a while.'
'That's Lord Murray of Pitkirtlyhill. Can I speak to him?'
Amaryllis made a thumbs-up sign to Charlie. He smiled politely.
'Hello?' said Amaryllis. 'Lord Murray?'
'No, it's me,' said Christopher. She could hear him wheezing even with the line being so bad. Why wasn't he in the ambulance? Had Jemima and Dave kidnapped him?
'Get off!' he added. She deduced that he wasn't speaking to her.
'Is Lord Murray there? I need to speak to him about Mal.'
'What about Mal?' Christopher sounded suspicious. He wasn't going to give up the phone without a struggle. She gave in for the sake of speed.
'Can you just ask Lord Murray if there's any previous connection between Mal and Pitkirtly Island? Any reason for him to want to –um – destroy it? And,' she added hastily, 'does he have any background in explosives? In the army, I mean.'
There was a pause, then Christopher said tentatively, 'He told me about it. In the ambulance. Mal got into trouble over some incident on the island. When he was younger. Something to do with explosives. And girls drowning. Then they sent him away to join the army... Get off me, you stupid dog!'
'Girls drowning?'
She heard a lot of coughing at the other end of the line, mixed with what sounded like whining, and then Jemima's voice. 'He can't talk any more just now. We've got to get him home.'
'Hmm,' said Amaryllis, cutting the connection. 'That makes sense. But it means he'll be more desperate to succeed. More dangerous.'
'What's that?'
She explained it to Charlie as best she could. In the end he shook his head and said, 'I'll never understand you, Amaryllis. You're still enjoying all this, aren't you?'
That was why, she reflected, she had some sort of a relationship – albeit a strange, flawed one - with Christopher, but could never have one with Charlie. Christopher accepted her without question: even when he strongly disapproved of some of the things she did, he knew it was her right to do them. Charlie had that urge that, in her experience, policemen and school teachers often had, to persuade or coerce people to behave in a way that met their own standards.
'I'll enjoy it when we catch up with them,' she muttered.