"Who did?"
She hesitated.
"Someone above them."
Marcus stared.
"Who?"
Elizabeth opened a small drawer and removed a folded photograph.
She placed it on the table.
It showed four people standing outside a military research facility.
Christopher was there.
General Brooks was there.
Elizabeth was there.
And beside them stood a senior military officer whose face Marcus recognized.
General Samuel Brooks looked down.
His expression became rigid.
The fourth person was him.
Marcus looked from the photograph to the general.
"You were there?"
Brooks slowly nodded.
"Yes."
"Then you knew my brother."
"I did."
"You knew he was alive."
"I believed he was dead."
Marcus's voice rose.
"How many people in this room have been lying to me?"
Brooks stood.
"Sergeant, I understand your anger."
"No, sir. You understand your rank."
Marcus pointed at the photograph.
"You stood beside my brother. You stood beside my mother. You knew about Sentinel. And you let me walk around for six years believing he was dead."
Brooks lowered his eyes.
"I was told the operation had been terminated."
"By whom?"
The general looked at Elizabeth.
She answered quietly.
"By General Thomas Caldwell."
Brooks's head snapped toward her.
"That's impossible."
Elizabeth shook her head.
"He's the one who authorized the original agreement."
Marcus stared.
"Who is Thomas Caldwell?"
General Brooks slowly sat down.
"Former director of military special operations."
Marcus looked at him.
"And where is he now?"
Brooks hesitated.
"He's currently serving as an adviser to the Department of Defense."
Marcus laughed bitterly.
"So the man who ordered all this is still in government?"
Elizabeth nodded.
"And he knows you're here."
What Rex was trained to find
Marcus looked down at the dog.
"Why was Rex sent to me?"
Elizabeth folded her hands.
"Because Rex was trained to recognize a particular chemical marker."
Emily frowned.
"A scent marker?"
Elizabeth nodded.
"Christopher discovered that Sentinel had been using a specialized compound to identify individuals who had undergone a particular medical treatment."
Marcus looked confused.
"What treatment?"
Elizabeth glanced at General Brooks.
Then back at Marcus.
"Six years ago, after Christopher's mission, you were involved in an accident."
Marcus frowned.
"I was twenty years old. I broke my shoulder during training."
"That wasn't the only thing that happened."
Marcus looked at her.
"What are you talking about?"
"You were transported to a military medical facility. Your records show that you received emergency treatment for an injury."
"Yes."
"But your original medical file contains a second procedure."
Emily leaned forward.
"What procedure?"
Elizabeth looked directly at Marcus.
"An experimental treatment designed to help soldiers recover from exposure to certain chemical agents."
Marcus shook his head.
"I never received experimental treatment."
"That's what your records say."
"Then the records are wrong."
Elizabeth nodded.
"Yes. They are."
She continued.
"Someone used your medical identity to authorize a procedure you never consented to. The treatment involved a harmless tracer compound. It was designed to remain detectable for several years."
Emily's expression changed.
"That's why Rex could identify him."
Elizabeth nodded.
"Exactly."
Marcus stared at the dog.
"So he was tracking me?"
"Not just you. He was trained to locate anyone carrying the same marker."
"Why?"
"Because Sentinel wanted to know whether the people connected to the original operation were still alive."
Marcus looked toward the door.
"Then why didn't Rex attack me?"
Elizabeth's eyes softened.
"Because Christopher trained him not to."
She reached down and touched the dog's head.
"Your brother taught Rex that you were family. No matter what happened, Rex was never to treat you as a target."
Marcus slowly crouched.
Rex leaned against him.
For the first time since entering the hospital, Marcus understood why the dog had refused to leave his side.