A few minutes earlier
Sam watched in suprise and disgust as Zachariah literally tore his skin off. He wished he could move his head so that he could look away. When Zachariah was finally stopped Sam found himself staring at his own face. "Much better don't you think?" He asked with a smirk.
Dean will never believe that you are me!" Sam argued but he was only 67% sure that was true. The shape-shifter laughed at him and closed his eyes seeing all of Sam's memories.

"Interesting it seems that I can read you like humans while you are a simple machine, " he mocked. "What's this I see you've grown to care for this human, " he continued.
"Yes and I won't let you trick him, I know what you are now, " Sam respond keeping a brave face. He remembered what Dean had told him about his past and how a creature called a shape-shifter killed his family using his own face. Sam was able to detect that this was in fact a shape-shifter. "You're a shape-shifter the same one that framed Dean, " he spat out.

"Well aren't you a clever robot, " Zachariah commented before making the lab go dark. "But you won't outsmart me, see you i've got a human to find, " he continued using Sam's voice. He disappeared and Sam was left in the dark unable to move at all. His scanners immediately began searching for a possible escape, he couldn't just sit here he had to save Dean. While working towards the device on his head, he could overhear Dean's voice from the other room.
"No, " Sam said to himself as he listened to the conversation. "It's not me Dean, "

Now
Something was wrong this was too easy, Dean realized soon after he had hugged Sam. He felt extremely cold and while Sam was a robot he always felt warm, plus since when did shape-shifters not tie up their prisoners. Testing his theory Dean stabbed 'Sam' across the back during their hug.
"Ouch what the hell Dean!?" Screamed the so called Dean. Immediately because of the reaction Dean knew this wasn't Sam, but Zachariah.
"Your not Sam!" Dean exclaimed pushing the shifter away from him.

Zachariah hit the wall with a loud oof but he recovered quickly. He stood up and gave Dean a burning glare.
"That hurt, " he said snarling through his teeth.
"It was meant to nice to see you again, " Dean responded cleaning off his silver knife so that all the blood was gone. "If I had known that my boss was the same shape-shifter who framed me, I would have done that years ago!" He declared.

Zachariah gave Dean a mocking smile and took out his weapon from his pocket. It was an obsidian dagger, a weapon Dean had never seen before.
"What's the matter De? Why suddenly so silent?" Zachariah mocked and before Dean could respond the shifter tackled him. "Just so we're clear you're so fired, " he whispered into Dean's ear and placed the dagger close to Dean's neck.
"I hated my job anyway, " Dean responded refusing to flinch or beg for his life.

"I knew you would run away so that's why I hired you when you came into my office, I saw the chance to take you out when you least expected it, " Zachariah explained to him. "But then I realized the worse thing I could do was make you forget who you were that way you wouldn't be a threat, " he continued. "I almost succeed but then that glitchy robot brought the old you back and I had to get rid of it to keep you down, " he finished. Dean struggled to move under the shape-shifter's grip but continued to stay strong.

"Ughhhh you creatures talk too much and Sam is more than a robot he's alive and for more human then you will ever be, " Dean responded and headbutted Zachariah until he was able to free himself. Dean groaned in pain briefly but brushed it off and made his move. He kicked the obsidian dagger out of Zachariah's hand making him defenseless and striking the shifter again with his knife. Zachariah growled angrily and tried to attack back but Dean was faster and cut him on his stomach. Zachariah dropped to the floor bleeding and Dean stepped on his enemy's wound until he admitted where Sam was.

"He's in the lab.." Zachariah groaned weakly. Dean said a sarcastic thank you before kicking the shifter. He messed with the old rusty doors until he got them open, and stumbled across the real Sam. He remained silent as Sam noticed him.
"Dean you're okay, " Sam said in relief. Dean had no words and remained silent as he helped Sam up. He took the device on Sam's head and crushed it allowing Sam to move again. "How do I know you're the real Dean?" Sam asked being cautious. While his scanners said it was they could be wrong.

"Sammy don't be like that, " Dean said to him trapping Sam in a hug. "If I was a shape-shifter you would be dead right now," he continued. Sam realized that it was really Dean and was relieved, he had to admit that being hugged by Dean was nice. He hugged Dean back and wished to stay that way until he could forget that this ever happened.
"How.. " Sam started but Dean caught him off.
"It doesn't matter now, I'm taking you home, " Dean told him.

Sam could agree to that statement and since he was able to walk again. It wouldn't  be much of a struggle, however as the two left Dean noticed that Zachariah wasn't on the floor anymore. "That can't be right he was bleeding to death, " Dean said in confusion. Right as he said those words he was once again tackled until he was against the wall, Zachariah was still alive, he was bleeding in multiple places but still alive.
"Not yet I'm not and I'm going to kill you with the last of my strength.. " Zachariah was cut off when a knife was struck into his heart.

He fell the ground dead and Dean was shocked to see that Sam had been the one to kill him.
"Sam?" Dean asked a little out of it. Seeing something like that just made his mind freeze up.
"I had to save you Dean, he was going to kill you, " Sam responded without a second thought. "You're probably mad at me but I couldn't let you die, " he continued hanging his head.
"Sammy I'm not mad at you, I came all this way to save you from that creature, " Dean answered immediately. He could never be mad at Sam for acting selfless, that's how he had always been.

"But why?" Sam asked. He didn't understand why Dean had come back to get him. "I'm a machine you could have just gotten a new me, " Sam knew that as a robot he was expandable. If he was gone Castiel would just built another him, maybe a better version.
"I don't want a different one, you're not expandable to me I.. you're worth saving, " Dean finally admitted.

He didn't know why it took him so long to admit that. Maybe because he had shut everyone out for so long. "Sam you need to know something, that I learned about you, " he continued.
"What?" Sam asked still a little shocked from Dean's words. 
"You're not purely artificial, you were created from the strand of a living being, you're alive, " Dean explained and Sam was left speechless. "That is why you're worth saving and even if you weren't alive I would still try and save you because you're family, "