Tonight’s The ABC Murders saw Hercule Poirot (played by John Malkovich) receive a number of letters from a killer who left clues about his upcoming murders.
As Poirot investigated the murders with Inspector Crome (Rupert Grint), another storyline centring around Mr Crust was unfolding.
Mr Cust (Eamon Farren) appeared quiet and unsuspecting but slowly clues began to drop hinting he was the killer.
He appeared in the Ginger Cat cafe where Betty Bernard worked and later at the bar she was at.
Mr Cust could be seen getting annoyed with Betty after she refused to pay for the stockings she had taken from him.
Later, as Poirot investigated Betty’s death, he found a pair of stocking around her neck.
The stockings were very similar to those which Alice Asher was wearing when her dead body was found prior to Betty’s murder.
It quickly became clear that the stockings linked the murders.
Now, adding fuel to the fire, Mr Cust star Eamon has dropped a huge hint he plays a “dark” character who doesn’t have a place in the world.
He teased: “When I first read the script I immediately felt that it was such a visceral world and the characters are so visceral themselves that I felt from Cust that he is a man at the pit of his very existence.
“He’s been through some experiences or events that have taken everything away from him.
“He is a broken and empty man and I felt that very powerfully in Sarah’s writing.
“I loved the idea of exploring someone who has nothing.”
Eamon continued: “He’s not seen nor heard and doesn’t have a place in the world.
“That is dark and very bleak.
“Within beauty there is always darkness and because of that, my job playing Cust is to find the beauty in his darkness and I love that.
“It’s very easy to play a horrible person or someone who doesn’t have any redeeming qualities but what’s more interesting is to think about why he is there and what that does to someone’s mind.”
The synopsis for the second instalment reads: “The ABC killer sends more letters promising to spill blood.
“Hercule’s past, integrity and identity come into question while he fights a rising tide of xenophobia.”
The ABC Murders continues tomorrow on BBC One at 9pm.