He was 38 years old. His name was Murat Karatas. The first hint of unease, friends said, was when Bacca did not check in by text message that evening with her fiance, Giovanni Chiari. They weren't unduly alarmed; after all, her phone battery could have died. But she did not answer calls the next day, or the next.
Local artists raised the alarm with Turkish authorities. Police began searching. By week's end, her family had appealed to the Italian Foreign Ministry for help. Officials there passed the message to Stefano Canzio, who has served as the Italian consul in Istanbul for seven years.
Days already had passed, so Canzio understood the matter's urgency and quickly brought his many contacts to bear. He arranged a Turkish-language appeal on the country's most-watched TV station. He conferred with senior law enforcement officials. He looked after Bacca's sister Antonietta and her fiance, Chiari, who had arrived to help with the search.
The blog that Moro and Bacca had used to describe their journey became a forum for appealing for information about her whereabouts.
"Pippa Bacca, dove sei?" it asked. "Where are you?"
The days wore on. The police were hunting intensively, but the search could be narrowed only so far. Although Bacca's planned route was known, and sightings of her confirmed, no one could remember seeing her get into a particular vehicle.
Then came the break police had been waiting for: Karatas used her cellphone to make a call, apparently not realizing that the signal could be traced even though he had thrown away her SIM card.
The authorities pounced. The road east out of Gebze, in the direction of the little village of Tavsanli, winds its way into verdant countryside, a nature reserve. Bacca would have realized that this was not the main highway to Ankara, the capital. But the driver could have lulled her with assurances: a shortcut, a detour.
In any event, she could have understood very little of what he said, or he her. Dressed as she was, this foreign woman might have appeared to him to be unbalanced, confused, vulnerable.
At times, the road twists in such sharp switchbacks that it would seem someone in fear for her life could have jumped from a slow-moving vehicle. Cars must pass one another so closely that a passenger could be seen if she screamed or gesticulated for help. But no one saw such a scene.
