'How did you know about the stone circle?' says Ruth.
Nelson is taken aback. He has retreated into his office and shut the door for this phone call and now he stands up and starts to pace the room.
'What do you mean?'
'A team from UCL were digging at the original henge site just before Christmas. They think they've found a second circle.'
'Is this one made of stone?'
'No,' says Ruth and he hears her switching into a cautious, academic tone. 'This is wood too. Bog oak like the other one. But they're calling it the stone circle because a stone cist was found in the centre.'
'What's a cist when it's at home?'
'A grave, a coffin.'
Nelson stops pacing. 'A coffin? What was inside?'
'Human skeletal matter,' says Ruth. 'Bones. We're waiting for carbon-14 results.'
Nelson knows that carbon-14 results, which tests the level of carbon left in human remains, are useful for dating but are only accurate within a range of about a hundred years.
He doesn't want to give Ruth the chance to explain this again.
'Why this sudden interest in the Bronze Age?' says Ruth.
'I've had a letter,' says Nelson.
There's a silence. Then Ruth says, her voice changing again, 'What sort of letter?'
'A bit like the ones I had before. About Lucy and Scarlet. It had some of the same stuff in it.'
'What do you mean "the same stuff"?'
'About corpses sprouting, shoots rising from the earth. Imbolc. The sort of stuff that was in Erik's letters.'
'But . . .' Nelson can hear the same reactions he witnessed in his colleagues earlier: disbelief, anger, fear. 'Erik's dead.' 'He certainly looked dead to me when we hauled him out of the water.'
'I went to his funeral. They burned his body on a Viking boat.'
'So it can't be him,' says Nelson. 'It's some nutter. What worries me is that it's a nutter who knows a bit about me. The letter mentions a stone circle. That's why I rang.'
'It can't be this circle. I mean, no one knows about it.'
'Except your archaeologist pals.'
'Actually, they've got funding for a new dig,' says Ruth. 'It's starting on Monday. I was planning to drop in for a few hours in the morning.'
It's Friday now. Nelson should be getting ready to go home for the weekend. He says, 'I might drop by myself if I'm not too busy. And I'd like to show you the letter because, well, you saw the others.'
There's another tiny sliver of silence and Ruth says, 'Isn't the baby due any day now?'
'Yes,' says Nelson. 'That might change my plans.'
'Give Michelle my best,' says Ruth.
'I will,' says Nelson. He wants to say more but Ruth has gone.