Previously: Jay's new partner Emily kissed him and he didn't pull back. Meanwhile, he has to think of a way to tell Erin. Erin is suspicious.

Erin had a slow day at work. Chloe was a fussy little toddler this morning and gave Erin a terrible headache. Usually Jay was there to calm Chloe down, but he went to work early.

Her day was going by terribly slow. The case her unit was working on had no leads and she just wanted the day to be over.

Erin was also distracted. She couldn't stop thinking about how weird Jay was acting last night. In all the years they have been together, they always opened up to each other when something was wrong. She thought about maybe it being her fault. He didn't even kiss her goodnight or cuddle with her like they regularly do. Erin doubted herself and blamed all of it on her. She thought maybe he had enough. All these thoughts were eating her alive.

On her lunch, she decided to go to the district and talk to him and find out what was going on.

On her way in, she ran into Kim. Kim squealed and hugged her tight.

"Hey Kim, is Jay here?" Erin asked, pulling away from the hug. Kim could see the worry in her face.

"Uh, no.. The guys left for lunch a little bit ago.. I assumed he was going to go see you? We missed you last night! Although I didn't stay long, had to take a drunk Adam home..." Kim said. So it wasn't Kim's perfume on Jay's clothes, Erin thought.

"I need to talk to him, how long do you think he will be?"

"He should be back soon. I will buzz you upstairs and you can wait for him, if you want?" Kim asked.

Erin nodded and Kim buzzed her in. As she walked upstairs to the bullpen, it was strangely quiet. She was expecting loud yelling and sarcastic jokes to be thrown at her. Instead, all she saw was a woman sitting at her old desk. Even Hank wasn't in his office. Kim walked back to the locker room leaving her alone with this woman.

Emily looked up when she heard footsteps. Emily took in the 5'4 brunette who was very intimidating and also very beautiful. She had some idea who this woman was.

"Oh, hi!" She said smiling cheerfully.

"Hi.. Um, where is everyone?" Erin asked.

"The guys decided to have a guys lunch.. Um, it's a slow day. Could use one of those after such a crazy night last night.." Emily said, grinning ear to ear.

Erin nodded, confused.

"Uh, you must be Erin, am I correct?" Emily asked.

"Yeah, and you are?"

"Emily Roberts.. I'm Jay's partner." She extended her arm to shake Erin's. Erin shook her hand and gave her a small, fake smile. "It's nice to finally meet you."

"You too," Erin said. "Um, I'm just gonna wait for Jay, hopefully he won't be long."

Emily nodded and Erin walked over to Jay's desk to take a seat. Emily looked her over really taking in the jealousy she had for Erin. Erin was fit and was absolutely stunning in a pantsuit. Emily was jealous that she had Jay and such a perfect life, as it seemed. The jealousy became overbearing that she had to burst Erin's bubble. Emily wanted Jay and after last night, she thought he wanted her too. She was going to break the news so he didn't have to.

"Erin, I need to tell you something." Emily blurted out. Erin looked up and nodded. Oh no, she thought.

"Last night, uh, I don't know how to tell you this but, Jay and I kissed.." Emily confessed. Erin sat there shocked. Her suspicions had been confirmed. Jay kissed another woman.

"We kissed and it escalated quickly to the point where I forced him off me.." Emily lied, Erin ran her hand over her face.

"I'm sorry Erin, I just thought you should know. Jay barely talked about being married or I would have broke it off right away."

Just as Erin went to say something, she heard laughing coming from the stairs. She quickly wiped the tears off her face and got up to leave.

The guys were too busy in their conversation to notice her run down the stairs past them. Jay was behind them and as she was making her way out of the precinct, she ran into him. He grabbed her and put his arms around her. He noticed her eyes were red and she had tears in them.

"Erin! What's wrong?" Jay said. Erin looked him into the eyes and shoved him away from her. He stumbled back a little and Erin ran outside to her car.

He ran after her and blocked her from getting into her car.

"How could you? After everything we have been through! You fucking kissed another woman!" Erin yelled, she was filled with anger instead of hurt.

"Erin, what are you talking about?! She kissed me!" Jay yelled back.

"Get out of my way!" Erin said sternly.

"No! Babe, talk to me. What did she tell you?"

"Nothing I already didn't suspect. I have to go." Erin yelled, pushing Jay aside so she could get into her car. She got into her car and wiped the tear that was falling down her face. Jay felt his world come crashing down. Erin was the most important person, besides Chloe, in his life. He hated seeing her so hurt. He knocked on the window trying to get her to answer, but she started the car and sped away. Erin had never felt pain like she was feeling now. She needed to be alone, at home. She called into her work and told them she needed to take a personal day the rest of the day.

Jay was left in a panic. This wasn't how she was supposed to find out. He should have told her sooner.

He stormed upstairs and went straight to Emily's desk.

"What the hell did you tell my wife?!" Jay yelled, causing everyones attention.

Emily gave a shocked face that was totally fake.

"I don't know what you're talking-"

"Stop! You told her I kissed you? You know that's not what happened! I pushed you off!" The whole unit gasped, shocked that Emily and Jay kissed. Jay was the most loyal husband.

"I don't think you remember correctly, Jay.."

"Oh stop it, I would never cheat on my wife! I have to go fix this.." He stormed off, grabbing his keys and phone. He texted Hank and let him know he was taking a personal day.

He drove to Erin's work and found her car wasn't there, so he drove back home. When he pulled up to the house, he found her car. She was here. His heart was beating fast.

He went inside and looked for Erin. When he went up the stairs, their bedroom door was locked and he could hear her crying. He could feel his heart shatter into a million pieces. He caused this. The last thing he wants to do in life is hurt Erin. She is his everything. She is his forever. And he may have just screwed that up.

He knocked on the door and tried to open it over and over. She didn't answer, just continued sobbing.

"Erin Kathleen Halstead, open this door, please! I need to explain... Please just hear me out." He begged. He waited a minute but she still didn't respond.

"Alright, looks like I'm just going to do this out here with a door between us." He sighed, thinking of the right way to tell her what happened.

"Erin, you know me. I would never, ever, cheat on you. Last night, I had too much to drink and so did Emily and she kissed me. I didn't pull back right away because I was drunk and stupid. I pushed her off and left. You have to trust me, I did not kiss her, she kissed me. Babe, I would never sacrifice our marriage. I love you so damn much." His voice was cracking by the end and, to his surprise, she opened the door.

She looked so hurt and angry, he couldn't blame her. He face was red from crying.

"I believe you. But, the fact that you didn't tell me... I knew something was wrong last night and you should have told me right away." She said, voice filled with anger. He went to touch her but she stepped back. She had to keep her guard up. He wasn't getting out of this so easy.

"Er, I didn't know how to tell you without you jumping to conclusions."

"Drunk or not, you still kissed her back and that hurts, real bad. We agreed to never keep things from each other and you broke that promise," Erin whispered, tears streaming down her face.

"I'm sorry-"

"Save it. I need time to think about this. I have to go get Chloe.."

"I can get her." Jay said, trying to make things easier for her.

"No, Jay. I'm staying at Hank's tonight." She said, moving past him to get Chloe clothes for Hank's.

"Erin, don't do this! I'm sorry, I love you.."

"It's just for one night.. I need space, to think... Away from you."

"Never walk away. That's in our vows, Erin. When things get tough we talk it through."

"Yeah, well not cheating wasn't in our vows because we knew we wouldn't cheat but look where we are." Erin said dryly, storming past him and leaving.