She walked back through the town to Hauptplatz, pausing on the Draubrücke to watch the Drava flow urgently beneath it on its long journey east from Italy. She was mesmerised as the water changed colour and speed by the second, and by the trees arranged like small forests on both banks, encroaching into the river itself.

She felt satisfied as she continued walking, pleased that she’d got somewhere and relieved that she didn’t have to involve the FSS at this stage. Once she was certain about the house, she’d tell Captain Hart. Until then, she was on her own. It felt safer that way. She couldn’t wait to tell Richard.

She’d been so taken with the river and so busy thinking through her plan for the next day, she didn’t spot either of the two men who’d been following her since leaving Frau Winkler’s – not the older one, tall with a short leather jacket, or the younger one, who looked like a boxer waiting for the bell to ring. It wasn’t entirely her fault that she didn’t notice them: both men were skilled at ensuring they weren’t detected – they’d grown used to their lives depending on it.

She didn’t spot them when they followed her as far as the FSS building on Hauptplatz, or when she emerged from the same building early the following morning and walked the short distance down the icy street to the bus stop. Nor did she notice them getting on the same bus as her when it pulled in before heading north, next stop St Nicholas’s church. By now the older man was accompanied by a woman.

Frau Egger was waiting at the bus stop outside the church, shoving aside a mother and child to ensure she got a seat. She was wearing the dark brown coat and black beret of the previous day, and looked dumpier and less elegant than Frau Winkler, untidy silver-grey hair poking from under her beret and a pair of spectacles held together by tape. She sat towards the front of the bus, a few rows in front of Hanne.

The bus made noisy progress through the town, and soon the lake came into view. A few passengers alighted at Annenheim, and when they passed a sign for Sattendorf, the vehicle slowed down and Frau Egger stood up and slowly made her way to the door. Hanne waited until it had stopped, not wanting to get too close to the woman she was following.

There wasn’t much to the village, which lay on the north shore of the lake: just houses, and what appeared to be a hotel or two close to the water. More houses were dotted on the hill rising on the north side of the road, with mountains looming high above them.

Frau Egger crossed the road from the bus stop and stopped to put on her scarf and gloves. She walked faster than Hanne would have expected, up a road with large houses arranged on either side, then turned right up a narrower road with only the occasional house on it. As the road became steeper, she paused once or twice but didn’t turn round. Hanne slowed her own pace, allowing the distance to increase between her and the older woman. It was bitterly cold; the air fresh from the lake and the mountains, and the sun cast the area in an almost blinding light. At one stage Hanne turned round and noticed a couple behind her, clearly hikers out for a day on the mountains. They didn’t seem to notice her.