I wanted to start with the things he had said about me to his wife (soon to be ex.)  He defensively denies he ever said anything bad about his son’s mother.  I explained again that she had all of this information about me that she could have only heard from one person.  He repeats, he would never say anything bad about his son’s mother.

I sat there jaw opened in shock for several seconds.  Seriously…  how do you respond to that?!  It’s simply not possible.  I shake out of it…  The therapist is just watching.  No expression.  I take a breath, and start again, “Another Event you can’t remember?  I can not believe that, and the simple reason is those words, those exact words are the ones I told you.”
Recap: It starts with a mouse, no it was a rat.  We heard it under the floorboards trying to gnaw in.  Our cats were on high alert and patrolling that particular corner non-stop.  It finally broke through one night and made it about six inches into the house.  That is as far as it went.  We heard terrible squeaking and we all went to check the noise.  Our small female cat sat smugly in the center of the room with the prize in her mouth, while the robust male cats looked disgruntled and defeated.  We were very proud of her, and we petted and praised her for defending the home.
My son made the mistake of telling this story at the dinner table at his father’s house years ago.  Somehow this story opened the door to other speculations about me; my cleanliness, my promiscuity, my morals, my worth.
I explained to the therapist that the hole was found, and repaired that night.  This happens every autumn when the weather changes, it’s usually mice seeking winter shelter.  The house we live in was built in 1887 with real wood floors, not like most modern houses that have concrete foundation; it’s just one of the drawback that come with 10 foot ceilings and Victorian trim.
She nods appreciatively and admits that she loves old houses too.
Anyways the comments about me continued.  It finally got to the point where my son told me he couldn’t take it anymore.  I had to confront his father.  I took him aside, insisted he give me a few minutes to talk about this issue.  I said I know that he held me in contempt, that much was obvious, but he had to see the affect that trash talking his son’s mother had on a kid.  Imagine if you overheard people saying that sort of thing about your own mother.  It’s one of the few things he really understood.  But those words…  those exact words are not something that he thought of himself.  They are the product of an issue I addressed in my backyard.  How is it possible that he still has those words, but no memory of the conversation that caused them?

My ex husband sees his opportunity and jumps in, that’s exactly why I told our son that he should not talk about things going on at your house or at mine.  He was always talking about you and your (current) husband.  I didn’t need to know that you guys were fighting and you were threatening to kick him out.
My eyes popped huge, mouth hung open again in disbelief.
“He said we were fighting?  When did this happen?”  He leans back getting comfortable, (he thinks he has me on the ropes now.)  It happened all the time, he says.   
“By fighting, you mean arguing?”  Oh yeah, he elaborates, you guys were screaming at each other and you were going to make the guy move out. 
“While the kids were home?”  He face drops into a look of absolute earnest, and he nods, saying that I was calling my (current) husband names and telling him he had to leave.
“I was doing this?  Yelling, screaming, calling names, threatening? “  I laughed.  “This is a non-reality.  This never happened.  First of all you know I don’t yell or scream.  You have even admitted it in this room.  You also know that I don’t call people names.  The other part that makes this transparently not true is the fact that I am very careful about what I expose my children to.  When my current husband and I need to discuss something we wait until the children are asleep or at school.  If they are home, we ask the kids to give us some time and we go outside to talk.”  No it’s true, he insists.  Our son said this when he was visiting.  He was upset about it. 
I look at the therapist.  She was working on her blank face skills that day.  “Okay, I’ll get him.  He is in the lobby; we can ask our son directly.  My current husband will be here soon too, we can bring him in.  This situation as you described it did not happen.  I am too discrete and aware of what I am doing to let that sort of drama unfold in front of my children.” 
Good place to pause.
Do you have any idea what is happening here?
If we step into the thinking of my ex-husband it makes sense: 

“She is making me look bad. 
She is saying that there is something
wrong with me because I can’t remember
her stupid story. 
I’ll show her.  I’ll tell a story she can’t remember. 
One that makes her look bad. 
She’s the problem, not me.”

This is the reasoning of a 3rd grader.
He has put me in a position where I am left with very few options.  The one thing I can say is:  You are lying.  This is why I cannot remember that event. (Note: I did not say this.)
Unfortunately for him, the last few years I have been honing skills to recognize this.  I have been studying manipulation tactics.  I have been researching Narcissistic Personality Disorder. 
This is a strategy.  If I say “I can’t remember because you are lying,” then it nullifies my claims against him.  In effect, he maneuvers me into giving a clear and logical alibi as to why he can’t remember.  Better yet, I would be the one who looks like the liar, since I used the word lying first.  I will be the “name caller,” the “accuser,” and that discredits everything I’ve said.
So how is it possible to have the emotional reasoning of a 3rd grader and the strategic instincts of a chess master?
I’ve asked myself this question a thousand times.  Does he know what he is doing?  Has he thought it out?  Or is this just instinct? 
I tried finding an answer.  My reading took me through Moral Development, and Freudian Projections.  They both kind of apply, but it doesn’t give a clear picture of what is going on inside of his head.  Then I came across the term internal temporal continuity.  Let me try to explain.
When most (healthy) people think about their past, there is a timeline.  They can tell the difference between the events that happened at 4 years old and events that happened at 10 years old, etc..  Most people can tell a story about how their feelings about certain things changed over time.  For example, as a kid I did not like certain vegetables, but as I grew older and started to cook I got excited about them. 
It shows a clear transition between:
feeling A) not liking veggies
and feeling B) loving veggies. 

Most people have this sort of memory access, because they are the same person throughout their entire lives.  They have grown and learned more, they have had life changing experiences, but overall, they are the same person inside.
Here is the disturbing part.  Narcissists are not; whatever person they were as a child never developed into an adult.  The Narcissist creates a false self.  Some psychologists call this masking, or personae.  As they acquire new targets for supply they fabricate new personae.  They lie the new identity into existence.  It happens spontaneously.  They start finding things out about the target and they custom build the new personae to match.  The target feels that this is the perfect match, a soul mate.

If you are like me and research as much as you can, you have read a lot of stuff like this.  Seeing how it applies to memory is a bit complicated.  Since they have not been the same person inside (Internal) and they don’t have long history of this persona (Temporal) they cannot have consistent memories (Continuity.)  What that means about my ex husband is that all the events of our marriage were erased from his memories as he developed a new personae to court the next target.  They\ only bits of information that he kept are the memories that made him feel good about himself, and the memories that he needed to seduce the next woman.  In this case, the dirt on me.
Now that they are divorcing, the memories of events with her are being erased, along with the overlapping memories.  This is how he can remember the rule “Don’t say bad things about his son’s mother” without remembering the event that caused the rule.

Okay, now to make sense of the story he came up with….
Back to Freudian projection.  He wanted me to look bad.  Recently he has learned (probably in his private therapy) that when couples fight and yell in front of kids, it’s very bad for the kids.  I think that I can safely assume that this is a value expressed by the new target (girlfriend or private therapist) and my ex husband is trying hard to incorporate this value into his newly generated history.  His new personae would instantly disassociate himself from acts that resemble what his target disapproves of.  He wants me to look bad, and he has memories of fighting and yelling that have not quite been erased, so he projects those actions on me to fill in a past event he has to answer for.

I get it… I see how it works, but what do I do in the situations when he is denying reality as it occurred and implanting false events?

At the end of that session I looked at the counselor.  I was so exasperated.  I wanted to cry. 
I told her that this is why I journal.  This is why I am so meticulous about keeping track of everything.  This is why I can’t throw away over 12 years of planners.  Because my reality doesn't exist with him.