Matt called Vic to confirm she was available and motivated to continue our experiment. Her boss had already answered to her request and allowed her to study the objects from the urn, including the lamp. I was glad she was enthusiastic to meet us at the depot in an hour, as Sir Guillaume was eager to perform—now we knew his secret.

In the stable-turned-garage, the knight eyed my motorcycle, asking me if it was as fast as a horse. I answered his questions with all the patience I could muster but was glad when the knight picked Lou's 2CV as transport, declaring he loved the cheery lime-green colour. Flattered, Lou allocated me the job of entertaining our ghostly passenger while he was driving. Matt drove ahead with the van, not trying to hide his gleeful grin.

Sir Guillaume bounced and fidgeted like an eager kid in the backseat, a place far too cramped for his considerable ectoplasmic bulk. He didn't mind in the least and simply slipped further back, half-disappearing in the upholstery of the seat while the tinpot sat on the bench beside him.

Lou studied the scene in the rearview mirror, frowning. "Just make sure you don't slip out of the car when I speed up."

Guillaume placed a hand on the pot's rim. "I'll hold on to this. It should work like an anchor."

"If you say so. Are we ready?" I nodded, and Sir Guillaume made a sound, not unlike a baby pig squealing, which Lou took for a yes. The car started with a cough, and we pulled out of the castle yard at a snail's speed.

Sir Guillaume gasped. "How fast can this carriage go?"

Lou sent me a lopsided grin and, instead of answering, accelerated. Taken by surprise, Guillaume held onto the chamber pot, now only his hands and lower arms visible inside the car while his body streamed out the back like a fluttering ribbon.

I leaned back to observe the spectacle. "Lou, slow down, or we might tear the poor fellow apart."

My friend braked to allow the knight to clamber back aboard. "Whoa. That was amazing. I saw these carriages many times on television, but you should have told me they go off like rockets."

"They don't. I guess you'll have to get used to it first." I rubbed my temples, trying to come up with an explanation for the paranormal physics at work. "Instead of being supported by the seat, your body slips right through it when the car moves. Perhaps you should concentrate more on the pot and try to keep your position in relation to it."

This trick helped, and soon Guillaume pressed his face through the closed side window to enjoy the view, only a hand placed on the pot's rim. I only hoped there were no speed control cameras set up tonight. It might be hard to explain why our passenger stood upright in the backseat at one point, torso passing through the car's roof, and arms spread out in a Kate Winslet I'm-flying pose.

Matt's van and Vic's ruin of a car parked already in front of the depot when we reached Avenches. It was high time, as Sir Guillaume wouldn't stop pelting me with questions about everything we passed on the thirty-minute ride. Obviously, the country had changed a lot since he last travelled it on horseback in the 13th century. I was exhausted and my voice hoarse when I greeted Matt and Vic and opened the door for Sir Guillaume.

The knight stepped out of the Citroën like royalty, his chamber pot tucked under one arm beneath his cape, and greeted our host with an elaborate bow. "Pleased to meet you, my lady."

I was sure if Vic opened her eyes any wider, her eyeballs were in danger of popping out of her skull. At least she didn't faint like Louis the day of his first encounter with Sir Guillaume.

I suppressed my urge to laugh and made proper introductions. "Sir Guillaume, meet Victorine Bourquin, guardian of the Roman artefacts of Aventicum. Vic, may I present Sir Guillaume of Corbières? He's our resident ghost and an honorary member and advisor of the Ghost Guard." Her eyes were still too round, and I felt more explanation was needed. "Sir Guillaume speaks Latin. We hope he can translate for Cinna."

Vic closed her mouth and scrutinised the knight from head to toe. "Wow. You believe the ghost—our white lady ghost—is the girl from the curse tablet?"

I shrugged. "My best guess. Let's find out, shall we?"

We followed Vic into the depot, Sir Guillaume inspecting the neighbourhood with the eagerness of a prisoner set free after a life sentence. Which wasn't too bad a comparison, considering he'd spent seven centuries enclosed in the walls of his castle.

As promised, Vic had brought the lamp, and it took her only a minute to fetch the missing piece from the shelf. Before she placed it in the slot, I stopped her and called for attention. "Right, does everyone know what we try to achieve? Sir Guillaume, I'd like to know why Cinna, if it's her, is still around and hanging out here. I'd prefer not to tell her straight away about the curse tablet but to hear her side of the story first."

"Understood." The knight bounced with eager energy like a kid the morning of his first day at school.

I longed to pat his shoulder, but didn't risk the contact. "Fine, then let's start." I pulled a thick candle from my pocket and lit it with a match. The sulphur smell recalled evenings by the fireside and Christmas. "Vic, would you mind switching off the lights?"

"On it." She walked to the entrance to turn off the bright illumination. With the mellow candlelight underlining the room's shadows, she slid the fragment into its slot on the lamp and placed the artefact on the same desk as yesterday.

From a safe distance, we watched and waited for the ghost's appearance. It didn't take long until the chill in the air announced the White Lady's arrival. Like the night before, a wisp of smoke formed and gained substance near the lamp first, then took the shape of a pale young woman with dark curls and deep-set eyes. She reached for the artefact without spending us a glance.

Guillaume placed his chamber pot on a desk with a clank, cleared his throat and stepped forward to perform his elaborate bow, translucent cape flying. "Salve, domina mea."

The ghost turned to study him, her fingers resting lightly on the lamp. Guillaume scratched his beard, waiting for an answer. But Cinna—if that was her name—seemed to lose interest in him fast and turned back to the only object capable of holding her attention.

I sighed, ready to intervene, but Sir Guillaume was not the type to be ignored. He pushed out his breast and spoke in a low timbre. "Ego Guillelmus de Corbières. Quid vocatus es, domina mea?"

Asking for her name was a good starting point. But the female ghost pulled her shawl closer around her shoulders and retreated a step.

"Cinna," I whispered, afraid I'd drive her away if I spoke too loud. The name caught her attention, though. She let the shawl drop to her shoulders, staring at me with her mysterious eyes.

"Cinnam sum." She repeated the name, her lips pulled into a dreamy smile. "Ubi Marius?"

Guillaume's brows rose in question. "She asks where Marius is. Do we know a Marius?"

Matt, Lou and I exchanged glances. This was probably not the best moment to tell her the man cursed her. Or was it? "Can you try to find out what kind of relationship she had with Marius?"

"Oh, you think he was her lover? I can try to dig for the details." A grin stole onto Sir Guillaume's lips. The knight seemed to be in his element. "Domina mea, Marius tuus dilectus est?"

This question had the effect of a magic key that made the fountain gush. Cinna showered the knight with a fast flurry of incomprehensible words. I had no chance to follow what she said. When she stopped, Guillaume tapped a finger against his nose. "Who called Latin a lingua franca? The woman speaks as if she were chewing on one of these pink bubbly globs the kids drop on the castle floors."

"Chewing gum?" Lou shook his head, a bewildered frown marring his face.

Vic chuckled. "I know what he means. For someone from the Middle Ages, the Roman girl must have a strong accent. A language evolves a lot in a thousand years."

Guillaume sent us a glowering stare and turned back to Cinna. With an amount of patience I'd never thought he possessed, he let the young woman repeat her statement phrase by phrase. When he turned back to us, his features were sombre. "Seems she was stabbed in the back while she offered a prayer to that heathen god Apollo. She asked for protection and health for her beloved Marius and something I can't understand."

"Does she know who murdered her?" My question triggered another length exchange.

In the end, Sir Guillaume shook his head. "She says she dropped her lamp when she was attacked, but she never got a glance at her murderer. At least that's what I gathered from the few understandable bits."

"If the lamp is the last thing she held or saw in life, it explains why she's bound to it. Like—" I interrupted myself before I made the comparison with Guillaume's tin pot. No need to upset him.

Matt's grin told me he got my meaning, anyway. "Can you dig for more information on this ominous Marius guy?"

Guillaume didn't seem to listen, his gaze hanging on the front door of the depot. An unnatural icy draft sent a shiver down my spine even before it opened.

Without forewarning, the ceiling lights bathed the room in their bright glare. Cinna's frail form dissolved like mist in the sun, and Sir Guillaume uttered a harsh curse, snatched up his chamber pot, and retreated into the corner behind Matt and Lou.

Paul strutted into the room, taking in our group before his gaze was drawn to the lamp and the candle sitting on the desk. "What are you up to? A seance?" His voice was sharp and his eyes were ablaze with fury.

"Good evening to you too, Paul." Vic's greeting was crisp, and she stepped forward, her arms crossed. "What are you doing here?"

He didn't bother to answer, but bypassed her, leaned forward, and reached for the lamp.

"Stop." I caught his wrist before he could touch the artefact. It felt like connecting myself to a live wire. Searing heat exploded in my veins while my heart hammered against my ribs in a hellish staccato. My world turned black.