The system lacks a stat specifically for lying to people.
In my own experience it has been used as a sub-skill of persuasion, and opposed by either your own ability to persuade someone, or with a notice check. A search if someone is actively paranoid about it, and says so. A search would also make the check considerably easier, similar to how it interacts with stealth. From there, it's up to the GM to modify it +/- based on how well the people know each other, and several of the perception modifiers could be applied, like if you can't see the persons face clearly for whatever reason.
As far as how to actually handle social lies, in my experience PC's are generally immune to the persuasion skill when used against each other. In the past, my group has had a player with problematically high persuasion skill. This caused a lot of tension and back and forth because his character was lying straight to our faces but backing it up with a massive number. In short, I would caution against overusing it. It occurs to me that this should be handled on a by campaign basis though, as a campaign centering around court intrigue for example would make this fairly important.
If you think the book is too abstract, consider making Bluff and sense motive into their own respective skills.
To quote the book:
Naturally, it isn’t possible to list all conceivable Secondary
Abilities. There is always a chance that someone will think of
a new skill that is not on the list. If this happens, the player
can seek the agreement of the Game Master to create that
new ability. To do this, it must first be determined which
Characteristic governs the skill. Such an ability will have the
same cost as others dependent on that Field. Of course, it is
necessary for the Game Master to approve the rules and agree
to the established advantages and limitations.