With the sun higher the sea wasn't so much blue any more as a panel-beaten silver sheet. Small fishing boats, moored off the beach, rocked on the dazzling surface in the morning's breeze. A passenger jet came in low above the river and banked over the cement works and beaches of Caparica south of the Tagus to make its approach into the airport north of the city-tourists arriving for golf and days in the sun. Further west and out to sea, a tugboat pulled a dredger alongside the Bugio lighthouse, Lisbon's scaled-down, antique Alcatraz. At the end of the wall a fisherman reached back with his rod, took two steps and sent his hook out into the ocean with a violent whip of his shoulders and flick of his wrists.

'She was hit hard on the back of the head,' said Fernanda, behind me. 'I can't say what it was yet but something like a wrench, a hammer or a piece of pipe. The blow propelled her forward and her forehead connected with a solid object which I'm ninety percent certain was a tree but I'll do some more picking around back at the Institute. The blow must have knocked her unconscious and would have killed her in time but the guy made sure with his thumbs on her windpipe.'

'The guy?'

'Sorry, my assumption.'

'It didn't happen here, did it?'

'No. Her left clavicle was broken. She was dropped from the harbour wall and I found this in her hair, in the wound.'

The sachet contained a single pine needle. I called a PSP officer over.

'Sexual assault?'

'There's been sexual activity but no evidence of assault or violent entry but I'll be able to tell you more later.'

'Can you give me a time of death?'

'About thirteen to fourteen hours ago.'

'How do you work that out?' asked Carlos.

His aggression got the full reply.

'I checked with the meteorological office before I came out. They told me the temperature didn't get much below 20°C last night. The body would have cooled at around 0.75 to i°C per hour. I recorded her body temperature at 24.6°C and found rigor mortis in the smaller muscles and just beginning in the bigger ones. Therefore my deduction, based on experience, is that you're looking for someone who murdered her between five and six yesterday afternoon but it's not an exact science as Inspector Coelho knows.'