tezmand
Like you, I was completely nonplussed through about 20 minutes of the show. At one point I even started thinking, "Did I miss last week's episode?"
And then it all began to fall into place. The girl who had her neck sliced in the cafe was the sister of one of the two blokes she was talking to. They were in the gang that supposedly kidnapped Ollie for the human trafficking ring, but it turned out that was just a ruse to expose the leak (who turned out to be the copper who had his throat sliced at the train station).
(SPOILER ALERT - DON'T READ ANY FURTHER IF YOU'VE NOT SEEN TONIGHT'S EPISODE YET)
Now that Ken Stott's character is out of the way, I don't know who the abductor could possibly be.
However, using the 'Miss Marple / Poirot' technique of it being the least likely person...I'm putting my money on the wife of the police inspector with the gammy leg.