Sheldon and Jo were in the lab talking over the new information they had discovered when they realized Mac was taking an awful long time in the bathroom. "I'll go check on him," Sheldon said and hurried to the bathroom. Of course, he discovered that Mac was not there. He came back out. "He's gone!"

"Oh no!" Jo said. She grabbed her phone and called Don Flack. "Don, get an APB out on Mac now!"

"I'm on it," Don said. "What's going on?"

"He's left the lab. He has been under some sort of hypnosis and he may not know what he's doing!"

"We'll find him."

Mac was at his apartment. He changed into a sweatshirt and jeans and put his coat back on. He knew they would be coming after him. He had to disappear until it was time for his rendezvous with his chosen one. She had told him he had to pick someone today. He had to finish that command. Mac stopped at the elevator of his apartment building. What was he doing? He looked back at his apartment. Just then, a sharp headache struck him. He grabbed his head as he heard the command again. Then he turned from the elevator as he noticed someone was coming up. He would go down the stairs…

Don Flack was in the elevator along with Danny Messer. "I hope he's here," Danny said.

"Chances are, he's either here or already left," Don replied. "I think he's on a mission."

"According to Sheldon, Mac has been hypnotized and programmed to do something and they don't know what."

"Why didn't they keep track of him?"

"He eluded them."

"Leave it to Mac to be clever."

They stopped at Mac's apartment door. "He told me not to kick his door in," Don said. "Should I ignore that right now?"

"I think this is a good enough time to say that Mac is not mentally capable of giving commands," Danny remarked.

"Right. I hope he agrees with that when he gets his mind back."

Don knocked on the door. "Mac! If you're in there, open the door!"

They listened but, of course, they did not hear anything. Don kicked the door open and he and Danny went in. They had their weapons in hand but not aimed. They went into Mac's bedroom. He had just dropped his clothes in the floor when he changed. "Looks like he's going somewhere," Don said.

"But where?" Danny asked.

"I hope we find out soon. There's no telling what they may have told him to do."

Don called Jo and told her that they had lost Mac. Jo looked at her watch. "I have to go home to be with Ellie," she said. "Call me any time there is a breakthrough in this no matter what time it is. I will call Russ and tell him to come over if I have to."

"Alright," Don said.

Danny looked around Mac's apartment some more but he did not find anything that would give any indication of what Mac was doing or where he was going. "I guess we'll just have to wait until he shows up somewhere," he said.

"Well, I hope it's not in some situation where we're going to find him dead or have to arrest him," Don remarked.

"Don't say that."

Mac was going down an alley toward his destination. He did not know why, but he had to finish what he had started. He kept wondering why he was doing this, but something was driving him and he had to. He could not resist. He did not want to feel another one of those headaches. He had heard the voice when he was standing there talking to Jo and Sheldon…Get away from them. They will hinder you from completing your mission. He had snuck out then and gotten away from them.

Suddenly, Mac almost ran into someone in the alley. "Hey, watch where you're going!" the man said.

Mac glared at him causing the man to back up. "Hey, it's no problem," the man said and kept on walking.

Mac continued walking on toward the woman he had chosen. She did not even know but she would know soon enough. He thought he had chosen her the first day anyway. After all, she was there around him all the time. Who else would he choose? It was getting dark now. Mac looked up at the full moon. He thought it was ironic that it was Halloween night but he supposed it was fitting. She should feel honored that he chose her…

With that thought, Mac stopped and almost felt dizzy. Honored? What was he thinking? He did not think he was such a great catch. Suddenly, another sudden headache almost took him to his knees. He stood back up almost sick. He had to keep going. Of course, she should be honored that he chose her…

Danny and Don were on their way back to the lab. Sheldon and Dr. Mitchum were trying to figure out what kind of programming Mac could be under and what he could be doing. "It seems that she was using some vampire theme on him," Dr. Mitchum said. "Perhaps she has him believing that he is becoming a vampire."

"A vampire?" Sheldon asked.

"Yes. Maybe he thinks he is going after his first victim."

"You mean you think…" Sheldon stared at the computer screen. "Can she actually do this?"

"There must be a key word or something that triggers him. What were you talking about when he left?"

Sheldon thought a moment. "We were talking about the case," he said.

"Can you remember anything specific that you said to him?"

"We were talking about the fact that these two sisters were the daughters of Rachel Wallace and she had been taken down by Mac. She was a psychic and was hypnotizing men and taking their fortunes and then having them killed."

"What else?"

"I told Mac that he couldn't be alone that he had to have someone watch him to make sure he wasn't taken over by some suggestion."

"What was the phrase that you actually used?"

Sheldon thought. "I said, 'you can't be alone'."

"Maybe that's it," Dr. Mitchum said. "Maybe that was the trigger."

"But why? How would these women know that we would say that?"

"Maybe they didn't. Maybe that was their trigger that they would use to get him later and you just happened to say it then."

"What does it mean though?"

"'You can't be alone'…" Dr. Mitchum considered that. "Maybe he is supposed to choose another woman. This woman had seduced him. It seems like this is all about humiliating him or causing him to do something he wouldn't normally do."

"You think he's going after a woman?"

"Could be. Does he have a girlfriend?"

"Not that I know of. He keeps that to himself."

"Any woman he is close to?"

"Well, he works with Jo every day."

"Maybe she is his target."

"Why her? They're not in a relationship."

"It may not matter. He might choose her because she is always around him."

"You could be right."

"You better warn her."

Jo heard her cell phone ring just as someone rang the doorbell. She went to the door and was shocked to see Mac there. "Mac, where have you been?" she asked.

"On my way here," Mac said.

"On your way here? Why?"

"Is anyone else here?"

"Yes, Ellie is here. Why?"

Mac stared at her a moment. "Can't I come in?" he asked.

Jo was uneasy about the way Mac was looking at her but she let him in. After all, she knew him. Mac took his leather jacket off and hung it on the coat rack. Jo watched him as he turned to her. She knew he had left the lab without them knowing where he had gone. "So, what brings you here?" she asked.

"You," Mac replied.

"Me?"

"Yes. I've chosen you."

Jo backed up as Mac stepped closer to her. "For what?" she asked. She wished she had answered her phone now. She knew that must have had something to do with this.

"My mate," Mac said.

"Mom!" Ellie called.

Jo gasped and Mac stopped and stared at her a moment. "What, Sweetie?" Jo asked.

"Who's here?"

"Mac is here. You remember him, don't you?"

Ellie came into the living room. "Of course," she said.

"Honey, go back to your room," Jo said. "Mac and I have some talking to do."

"Okay."

When Ellie was gone, Jo looked at Mac. "Just what are you doing?" Jo asked. "What do you mean, your mate?"

"I think you know what that means," Mac said.

Jo remembered that her phone was in her room on her bed. She wanted to get to it but she did not particularly want to lead Mac into her room, but if she could get the phone, she might get some help. "Why don't we talk about this?" Jo asked.

"What's to talk about?" Mac asked. "You've always had a thing for me."

Jo looked shocked. "And just where did you get that idea?"

"I can tell."

Suddenly, Mac stopped and seemed to waver. He looked at Jo as though he did not know where he was. "What's going on?" he asked.

Jo realized Mac's own nature was trying to take over. "Mac, you are under a hypnotic suggestion," she said. "You have to fight it."

Mac looked at her. "I can't," he said. He suddenly grabbed her and kissed her.

Jo tried to push him away and finally got away from him. Then she ran for her room. By the time she got in the door, Mac was there too and he shut the door and locked it. Jo ran to get her phone and started to dial the number, but Mac came and grabbed her hand. "No," he said.

"Mac Taylor, you let go of me," Jo demanded.

Mac stared at her a moment as though he did not know where he was again. "Mac, listen!" Jo said. "You can't do this!"

Mac grabbed his head. "Jo, help me," he begged as he fell to the floor.

Jo squatted beside him as she called Don Flack and told him what was going on. "We're on our way!" Don said.

Jo ended the call and knelt beside Mac. "Help is coming," she said.

"I'm sorry, Jo," Mac said.

"Don't you worry about that." Jo put her arm around Mac. She knew he would never do such a thing. His true nature took over.

Mac lay down in the floor. "I think I'm dying," he said.

"No you're not. That's what she wants you to think."

Mac stared at the ceiling. "Victoria," he said. "That was her name. She did this to me."

"We're going to find those two women and we're going to get help for you," Jo said.

"I'm sorry."

Jo touched his face. "Stop apologizing," she said. "I already forgave you."

Mac closed his eyes and Jo thought he was asleep, but suddenly, he opened his eyes and grabbed her again. Jo found herself lying on her back on the floor and Mac was over her. "Mac, snap out of this!" she said.

Don and Danny were going toward Jo's apartment with the siren blasting and Sheldon and Dr. Mitchum were coming that way too. They knew Mac was going to need some help.

Jo had gotten away from Mac again and was on her feet. "Stop right there," she warned. "Or I will hurt you."

Mac glared at her. "You can't beat me," he said.

Jo showed him different when he came toward her again as she kicked him in the groin. She grimaced herself as she hated to do that to Mac but she did not see any other choice. That seemed to make him angrier though. He lunged at her and they were in a struggle that landed them on the bed. Jo hoped Don and the others would get there soon. She was not sure she could hold Mac off. He was strong after all.

Suddenly, Jo heard Ellie knock on the bedroom door and say, "Mom, are you okay?"

Jo looked at Mac. "Mac, stop this!" she whispered. "Ellie is right out there."

Mac wavered a moment but then he continued trying to get Jo where he wanted her. She slapped him and then tried to crawl off on the other side of the bed but Mac grabbed her around the waist…

Don and Danny were coming down the hall of Jo's apartment building. "Remember, there's a child in there," Danny said.

"We'll get her out of there first," Don said.

Don knocked on the door as they got to it. "N.Y.P.D.!" he said.

They heard the door unlocking and Ellie was there. "I think Mom is in trouble," she said.

"Come with me," Danny said and took Ellie down the hall.

Don went on into the apartment. He could hear a struggle going on in the bedroom. He hurried over to the door and got ready to go in but the door was locked. Suddenly, he heard a gunshot. Don kicked the door opened and aimed his weapon inside. Jo was standing with her weapon aimed at Mac. She looked like she had been in a fight and so did Mac. "I tried to get him to stop," Jo said.

Don looked at Mac who looked like he was in another world. He turned his gaze toward Don. "Mac, give up," Don said.

"Why?" Mac asked.

"This is not you! You can't do this."

Just then, Sheldon and Dr. Mitchum walked in. "Mac, just relax," Sheldon said.

Mac looked like he was surrounded. He backed up as he realized they were all trying to stop him. Then he stared at the floor as though he were listening to something. He looked at the window in Jo's bedroom. "NO!" Sheldon exclaimed.

Mac looked at him. "You can't do that!" Sheldon said.

Mac ran for the window. "NO!" Don yelled as he realized what Mac was about to do.

Luckily the window was locked so they got to him before he could get it open. He would not let go of the window, however. "Let me go!" he yelled.

"Not on your life!" Don said.

Mac was trying his best to get the window open as Don, Sheldon and Jo were trying to hold him back. Dr. Mitchum was getting a syringe ready with a sedative. "Hurry!" Sheldon said as he saw Mac pulling the lock on the window back. "Stop, Mac!"

"NO!" Mac screamed. He got the window unlocked and tried to push it open.

Dr. Mitchum had the sedative ready and got over to the fray. "NO!" Mac cried as he felt the pinprick in his neck. He felt himself go limp as he fell backward into the arms of his friends.

"You'll be okay," Jo said with tears on her face.

"I'm sorry," Mac said as he fell asleep.