Spoiler warning! If you haven't watched last night's show, maybe skip this one for now. 

The identity of a fourth killer was revealed in the second episode of BBC One reality competition show The Traitors.

Amongst the 22 contestants taking part, including a self-described clairvoyant and a disability model, is Harry, a British Army engineer from Slough.

The 22-year-old corporal says he wants to be a traitor as he is a bit of a “Jekyll and Hyde”.

During the first episode of the second series, the show’s host, Claudia Winkleman, announced a surprise twist and said the three “traitors” she had chosen would get to enlist a fourth member.

During Thursday’s episode the fourth traitor was unveiled as veterinary nurse Miles, 36, from Birmingham, who joined the other killers at the traitor turret, which is where they plot to kill off the “faithfuls”.

The first three traitors had been chosen by Winkleman in Wednesday’s episode and are business manager Paul, 36, from Manchester, British Army engineer Harry, 22, from Slough, and events co-ordinator Ash, 45, from London.

Paul said: “Miles being brought in has strengthened us an unbelievable amount, he’s a big personality, strong willed but he’s also fiercely loyal.”

Also in the episode, the first murder victim was revealed as retired shop owner Aubrey, 67, from Loughborough, Leicestershire.

The contestants realised that he was missing when he failed to turn up for breakfast.

In a clip that showed them deliberating who to kill, Harry said they should chose Aubrey as “it throws them off our scent”.

After this the group deliberated on who they should banish, and volunteer business mentor Sonja, 66, from Lancashire left the castle after she received the most amount of votes.

Before she left she told the contestants she was a faithful and said: “Well guys, facts are important to me as they obviously are to you.

“So here’s a fact I would now like to confirm to you, and that is that I am a faithful.”

At the end of the episode the traitors regrouped to decide on who they would like to murder.

To win, The Traitors players must avoid being murdered or banished, which happens when contestants suspect a player is a traitor.

When the competition draws to a close, the few remaining players will share the prize pot if they are all faithful.

However, if there is still an undetected traitor among them, the traitor will walk away with the entire amount.

Throughout the competition, contestants will build up the cash pot through playing a series of games.

The Traitors continues on Friday on BBC One and the first three episodes are available on BBC iPlayer now.