[Ray.]

Beyond a gut feeling (which points me towards the unnervingly gangly Ellie ), the only one who's given me anything approaching a hint as to their potential for being the secret traitor, is Fiona. Her little asides to the viewing audience about her not being the dim Welsh gal they all take her for, and more importantly, her being so blasé about the possibility of finding a shield, gave me a bit of pause and made me think of Francis Urquhart in House of Cards.

Though Sam's wording about how he's confident the others 'believe' he's a faithful (as opposed to simply thinking he's one) is also potentially damning.