The young actress, who plays Morgana, told Digital Spy that she hopes the ending will be resolved by the BBC commissioning further adventures.
"We've left all of our characters on such a cliffhanger that you'd feel it wasn't finished unless you got a chance to see them through," she said. "Especially my character, because all her best stuff is yet to come. It's a show that's only going to get better!"
On the subject of a second season, McGrath revealed that the cast are optimistic but unsure, saying: "Obviously we hope it's going to go ahead. We don't know yet though, to be honest with you. For me I'll be very disappointed if it doesn't go ahead."
> Click here to read our full chat with Katie McGrath
> Click here to read our review of the latest Merlin episode