So... wait until there are more foreigners there.
Or wait until your target is the foreigner.
Or until there are people from several different realms there.
Or until a well-known infiltrator is also in the region.
If you set yourself up as the only logical culprit, then you deserve to be the only one everyone suspects.
My biggest issue with this argument is that the higher the "plausible deniability", the higher the risks, because these extra nobles usually have troops that will interfere with your activities.
Secondly, that plausible deniability is not important. The invisible status wasn't useful because it protected your identity, it was useful because it covered your tracks. You couldn't be actively hunted down and followed. In most cases, you are acting against enemies. If you are, who cares if you are identified? You are already an enemy to them. The main cases where you would care not to be identified are against targets that the game does not reward attacking: friends.
