Cato puffed irritably. ‘I can’t. Not yet. Unless he’s some kind of double agent … What if he were?’ Cato’s mind suddenly raced ahead with the suggestion. ‘Now that would make sense of things. The question then becomes which side is he really working for and which side is he misleading?’ He recalled what he knew of the recently promoted centurion. ‘He returned to Rome from exile about the same time as Agrippina. Perhaps he’s working in her interests. He could be posing as a servant of the Liberators to use them to help Agrippina and Pallas …’ A sudden flash of inspiration fired Cato’s mind. ‘Yes! That would make some sense of what happened this afternoon. The Empress and Pallas intend to wait until the Liberators have removed Claudius and then seize power. When she has what she wants and Nero sits on the throne, she can use the intelligence gathered by Tigellinus to move against the Liberators.’ He paused and smiled. ‘Clever, very clever.’

‘You’re looking very pleased with yourself,’ Macro said drily. ‘Maybe you’re right but that doesn’t help us to discover how the Liberators are intending to do away with Claudius.’

‘I know.’ Cato’s expression resumed its earlier weariness. ‘All the same, I must let Narcissus know about my suspicions as soon as possible. If I’m right, then the threat to Claudius is greater than Narcissus knows.’

‘After today’s dowsing, I think Narcissus might just be thinking that already.’

Cato laughed. The sensation felt as if a burden had been lifted from his mind. He realised how exhausted he was. Aside from the strength-sapping struggle against the body of water that swept him away and down the river, Cato was covered with scratches and bruises from the battering he had endured in the process. He needed rest badly, and looking at Macro he could see that his friend did too.

‘The hour’s late. We should get some sleep.’

Macro nodded and they rose stiffly and made their way out of the mess. They exchanged nods with the men still playing dice and then closed the door behind them. Outside a long colonnade led to the stairs up to the second storey. They had passed the centurion’s quarters and office and then the first of the section rooms when they saw a figure by the foot of the stairs pace slowly towards them. The man’s features were indiscernible. He stopped ten feet away, blocking their path. Cato strained his eyes and could just make out that the man was covered in mud. He wore a tunic and boots and his dagger scabbard was empty. His sword hung against his left hip, as was the custom for officers. Cato swore a silent oath and stood to attention.

‘Centurion Tigellinus. Sir, I thought we had lost you.’

‘Tigellinus?’ Macro began, then snapped to attention beside Cato.