Page 119 of Fire Must Burn

‘I think I can crack the book code for the messages hidden in Danforth’s flat,’ she said. ‘Would that be of interest to you?’

‘Tell me how you got this number first.’

‘I was with Edwards when he rang you from the hospital, remember?’

‘He’s not supposed to let you see him dial.’

‘He didn’t,’ said Sparks. ‘But I know how to identify the numbers by listening to how long the dial takes to return to position. Satisfied?’

‘Useful trick,’ he said. ‘Fine. Tell me about the code.’

‘It’s Thucydides, but you had the wrong translation and edition,’ she said, pulling out her notebook. ‘You were using the Crawley. Try the Jowett translation instead.’

She read off the publisher and edition.

‘Got it,’ he said. ‘I’ll send a man out to get a copy and see if you’re right. Where did you find this book?’

‘I’m not telling you until you verify that it’s the right one,’ she said. ‘I’ll call back in a few hours to confirm.’

‘Sparks, either you tell me right now, or—’

She hung up, then leaned her forehead against the telephone.

‘Promise you’ll visit me in prison,’ she said.

‘I expect they’ll let us share a cell,’ said Gwen. ‘What’s all that about a book code?’

‘Both parties need to have the same book. Then you use two numbers to locate a word. The first is the page number, the second is how many words from the start of the page. The process is tedious but impossible to crack without knowing which book it is. They found coded messages in Tony’s flat after the fire that appeared to be encrypted by that method.’

‘That sounds rather incriminating,’ said Gwen.

‘Very,’ said Iris. ‘Miss Lowle suggested they try the edition of Thucydides that he bought at Maggs Bros, but it didn’t work.’

‘Why not?’

‘If I’m right, it’s because she faked those coded letters herself and planted them to be found,’ said Iris. ‘Only she used the wrong edition and translation. She must have assumed he bought the newer version. I found a copy on her desk.’

‘You are a wonder, Iris Sparks,’ said Gwen with a grin. ‘Now, if it’s a match, what then? Do you think the Brigadier will absolve Tony?’

‘Maybe,’ said Iris. ‘Maybe he’ll only give Lowle, or Charlotte, the sack.’

‘What do we tell Parham, then? He still has a case to solve.’

‘And solve it, he shall,’ said Iris.

She dialled another number.

‘Detective Superintendent Parham, please,’ she said. ‘Miss Iris Sparks calling.’

She was connected a moment letter.

‘Miss Sparks, good morning,’ said Parham. ‘Do you have something for me?’

‘I do,’ she replied. ‘Is PC Godfrey your fingerprint man on the Danforth case?’

‘He is.’

‘Send him to Grenville House. Tell him to fingerprint the door to the roof there.’