The first full trailer has arrived online for thriller The Guest, starring Downton Abbey‘s Dan Stevens as a mysterious stranger who ingratiates himself with a bereaved family.

Arriving out of the blue, Stevens’ soldier introduces himself to the Peterson family, claiming to be an old friend of their son, who was recently killed in action.

However, having welcomed him into their home, things soon turn nasty, as Stevens’ presence become linked to a series of supposedly accidental deaths…

Take a look at the new trailer, below…

Directed by horror regular Adam Wingard, this one looks genuinely creepy, and offers a great change of pace for the usually foppish Stevens, who makes for a pleasingly ambiguous lead.

Co-starring Maika Monroe, Lance Reddick and Leland Orser, The Guest will open in the UK on 5 September 2014.