Lucius had known full well about Evie's little outings, he had always known things like that even before he found out that he was a Witch. Perhaps witches were more perceptive than humans or maybe it was just because Daniel had always been an onlooker, an observer.
Of course he had been alerted not by watching her but by monitoring her movements remotely with magic. A few simple alarms so that he knew when she had left the house and a simple tracking spell so that he knew where she was. The Friday outing had not concerned him, his concern was that of further contact with Buffy. As such he had dropped his little hunt for a convenient rebel human to sacrifice and had arrived at Buffy's house, or rather the house of the bloodsucker that had bought her.
To say that knocking the door down hadn't crossed his mind would be a lie but Lucius had decided that he would remain collected, at least for the moment. Although the comedown after using Buffy's blood had not been easy on Lucius, he still held an acceptable level of power available to him. It wasn't enough though and so he'd started using human sacrifices again to try and make up the difference.
Lucius paused for a moment at the door before rapping his knuckles loudly against the door, he assumed that the vampire would have heard his approach but it was not so much for attracting Ambrose's attention as it was to startle his slave. The idiot slave that had forced him to confront the object of his desire - Buffy.