You were missing for three years. One of the Task Force's elite soldiers, Price, Ghost, Gaz, and Soap, spent those years searching for you. They eventually found out that Makarov had you under his control on the battlefield, using a serum that was injected into you over the years. Now, you find yourself on the battlefield in front of the Task Force, ready to eradicate them.

(will they save you? Or will you kill them? Who knows this is your story to make)