Merlin Missing

“What is that?” Merlin said as he stormed further into the room.
Arthur looked back and the between the two Merlins in disbelief.
“My god,” Gwaine exclaimed.
The Merlin who claimed to have no memory glanced back and forth between everyone’s faces. The other Merlin kept his eyes fixed on him.
“Who are you?” Merlin asked.
“I- I’m you. I’m Merlin,” he answered.
“No you’re not,” Merlin said. “Why do you look like me?”
“I don’t know! The only thing I can remember is waking up in the forest and finding your friends. I don’t remember anything else!” the other Merlin panicked.

Why are there two Merlins in Camelot? Will Arthur and Gaius be able to uncover the truth?