A/N Thank you so much for the reviews. I really look forward to reading your input. I still own nothing.

***********July 12, 2015, 6:20 P.M. Pacific Time************

Before Leonard3 could say anything, Sheldon1 quickly said, "I know you are wondering what has happened. Come with me and I will explain everything."

Still dazed, Leonard followed after him. As they walked, Sheldon wondered if he should try to reach Penny but decided he would learn more before he did. Having another Leonard show up could affect her in different ways.

Reaching Amy's office, they went inside. Sheldon quickly said, "Amy, we need to get out of here now."

Amy was startled, "What's going on? What is Leonard doing here?"

"I will explain in the car."

"All right. Just let me put this stuff away."

With Leonard still stunned and Sheldon obviously impatient to leave, Amy quickly finished up.

When they reached the car, Leonard got in the back seat with Sheldon riding shotgun.

As they pulled away, Amy said, "Okay. Are you ready to tell me what this is all about?"

Sheldon sighed, "Could we wait until we get to the apartment?" Seeing her look, "Please, you have to trust me."

The moment they were in the door of Apartment 4A, Amy said, "Well?"

Leonard was looking around in amazement. What had happened? The apartment looked entirely different. Where was Sheldon's stuff? It looked like there was a woman's stuff there.

Sheldon said, "Let's all sit down."

When they were seated, Sheldon took a deep breath, "Leonard, I know you are going to find this difficult to believe or accept, but you have been transported to a Parallel Universe."

Before Leonard could answer, Sheldon turned to Amy, "It appears we have switched Leonards again."

Amy just stared at him.

Leonard finally found his voice, "You are saying this is a different Universe?" How did I get here?"

Sheldon sighed, "I wish I knew." He then told him what had been happening, about how their Leonard had disappeared and been replaced. How now apparently it had happened again with him and the other Leonard." Sheldon smiled, "Perhaps we should start numbering our Leonards."

He smiled at Leonard, I guess you are Leonard number 3."

Amy spoke up, "Sheldon, what do you think happened to the other Leonard?" She hesitated, Leonard number 2."

"I assume he has traveled to another universe. Back to his own, another one, who knows?"

Leonard broke in, "So you are saying that a bunch of Leonard Hofstadters are bouncing around from one Universe to another?"

Sheldon nodded, "Crudely put, but yes."

He then went on, "Do you mind if I ask you a few questions?"

"Not if I can ask you some."

"That's fine, but you may not need to after you answer mine."

He started, "What do you do for a living?"

"I am an Experimental Physicist at Caltech."

Sheldon was a little surprised, "So is our Leonard."

"What do Amy and I do?"

"You both work at Caltech, you are a Theoretical Physicist and Amy is a Neurobiologist."

"Fascinating. That is true in our universe too."

"What relationship do you have with Penny?"

Leonard stared at him, "Penny? Who's that?"

Sheldon looked at Amy who was as stunned as he was. Sheldon was now glad he had not called Penny.

Sheldon managed a smile, "In this world, she is your wife."

Leonard was stunned, he finally got out, "I'm married?"

"You're not married to anyone?"

"No."

Sheldon nodded and then asked, "How about me? Am I in a relationship?"

Leonard smiled, "You and Amy are boyfriend and girlfriend."

Sheldon accepted that, "In this world we are married."

Leonard looked around, "Do you still live here?"

"No, you live here with Penny. Amy and I live in 4B."

They all sat for a while, trying to absorb what had happened.

Finally, Amy said, "Leonard, let me clarify something. You do not know anyone named Penny in your world?"

"Not that I remember."

She got up, "Perhaps if I showed you her picture."

She walked over to the refrigerator and took down a picture of Penny and Leonard.

When she showed it to Leonard, he was about to say he didn't know her, shocked at seeing who he was married to. Then he looked closer and was stunned. It couldn't be.

Seeing the look on his face, Amy said, "Do you know her?"

He looked up at her, "There was this woman. She looks like her but she had black hair and said her name was Carol." He looked back at the picture, "It can't be her."

Amy took back the picture, "I am sure there are women who look somewhat like Penny. How did you know this Carol?"

Leonard decided they did not need to know he had visited a prostitute. "Just a girl I met."

Penny had just come back from a ride. Coming home had been a good decision. Oh, she still deeply missed Leonard and wondered if she would ever see him again, but the pain had lessened being away for everything that reminded her of him. But, she knew she couldn't stay here forever. At some point, she would need to face the fact he was gone. She couldn't imagine ever being with someone else, but she also knew Leonard would not want her to spend her life waiting for him.

And then there was her job. She knew she had pushed being away as long as she could. Especially as she couldn't tell them what had really happened.

She had told them and her folks the same story, that she and Leonard were having problems and decided to separate for a while. Her parents had offered to help but she just told them she just needed to get away.

Just then her phone rang, she saw it was from Sheldon. They usually talked every other day, staying in touch.

"Hey, Sheldon."

"Hello, Penny." He hesitated, "First of all, I need you to know that our Leonard has not returned. But something has happened."

"What is it?"

"The Leonard that replaced our Leonard has been replaced with another Leonard."

"What?"

"We now are dealing with what we have decided to refer to as Leonard number 3."

"Damn it, Sheldon, what's going on? I don't know if I can handle this."

"I know, Penny." He sighed, "I need to tell you, this Leonard says he does not even know a Penny."

"Listen, Sheldon. I think I need to get back to Pasadena. I don't know why, but I need to see this guy. I know it won't help but I need to do something."

"Very well, Penny. We will be waiting."

A few days later, Sheldon and Amy met Penny at the airport, having decided it would not be wise for her to meet Leonard in a public spot, not knowing how she would react.

On the way back to the apartment, they talked about Penny's family and her trip.

When they reached the door of the apartment, Penny almost chickened out. But she gathered herself and they went in. As the entered, Leonard stood up. He and Penny's eyes met and she managed to say, "Hi, I'm Penny."

Leonard was stunned, seeing her in person, seeing how she moved, hearing her voice, he suddenly realized this was Carol.

Seeing him staring at her, Penny said, "Are you alright?"

Before he could stop himself he said, "You are Carol."

When Penny just stared at him, Amy broke in, "Are you sure? Didn't you say she had black hair?"

Penny found her voice, "Who's Carol?"

Amy turned to her, "When he said he didn't know a Penny, I showed him your picture. He said you looked like someone he knew named Carol, but she had black hair. He finally decided it wasn't you."

She turned to Leonard, "What changed your mind?"

"Seeing her in person, hearing her voice…"

Penny was still puzzled, "Who is this Carol?"

Leonard didn't know what to say. He didn't want to tell them Penny was a prostitute in his world.

Sheldon interrupted, "Leonard, if you are hiding something, please let us know. We never know what could be important."

Leonard sighed, "I know it isn't you." He hesitated and took a deep breath, "She was a prostitute."

There was a long awkward silence, until Penny finally got out, "You're telling me that in your universe, I am a prostitute?" After a pause, "How did you know her?"

Leonard blushed and lowered his head.

Penny's eyes widened and she said, "Oh."

For some reason, Leonard wanted her to know, "I didn't sleep with her, I had just paid her when I ended up here."

Penny just stared and then to everyone's amazement, she laughed. Finally, she said, "I hope you don't think I am going to take over for her."

Leonard turned red, "No, No. Of course not…"

Penny smiled, "Why don't we all sit down."

After everyone was fortified with a drink, Penny turned to Sheldon, "Well, Sheldon, what do we do now? Do you have any more of an idea what is going on?"

Sheldon sat up, "Actually, I have proposed a theory. I have nothing to back it up but it could explain what is going on."

"Each time a Leonard has shown up, the other Leonard has appeared to have disappeared. Now it is possible they are somewhere else in this Universe," He hesitated and said quickly, "Or gone." Seeing the look on Penny's face he hurried on, "But the most logical explanation is that they are moving between Universes, each replacing the other."

Penny put the thought of 'or gone' out of her mind and concentrated on what he was saying. "So you think my Leonard is in another Universe?"

"That would make the most sense."

Penny contemplated that. Was he with another Penny? Neither of these two Leonards had been married to her, but it was likely they were on some universe. Had he… No, she needed to believe that with all this, Leonard would not cheat on her, no more than she would on him.

She turned to Sheldon, "So, what do we do? Wait for our Leonard to come back to our Universe. If he does, will he then go off again? Like some Flying Dutchman?"

Sheldon smiled, "I am surprised you know that reference." He sighed, "If that is true, then we really have no hope. I would rather suggest another scenario. That each of the Leonards will at some time return for good to their own universe."

Penny considered that, "But didn't you say there are an infinite number of such Universes? How long could it be before he hits ours again. If he ever does."

Sheldon sighed, "I suppose that is true. But some scientists including Steven Hawking, believe there may be as few as five or ten Universes."

Amy broke in, "I have been thinking. It is true that there was not a lot of time between the transfers. What date was it when Leonard disappeared and Leonard number 3 appeared? In other words, how long was Leonard number 2 here?"

Sheldon thought, "Let's see, Leonard disappeared on June fourteenth. This Leonard appeared on the twelfth of July. So that would mean twenty-eight days."

After thinking a moment, Sheldon smiled, "If I were into religion like my mother, I would point out that the number 28 is an important number in the Bible. You can look it up on the internet. According to her, it shows up in a large variety of ways."

He went on, "There is also the fact that in Numerology, Angel number 28 means that you need to seek out another door to open in your life."

Penny stared, "Like a door to another Universe."

She went on, "So, in twenty-eight days they will switch again?"

Sheldon shook his head, "Penny, Penny, there is no scientific basis for believing that will happen."

Penny says, "I don't care, I want to believe it."

Amy smiled, "On August ninth, we'll find out."