So the scientist with glasses from the Lab place was in cahoots with the killer and saw his wife who had escaped from the killer's clutches running along the road, and took her back to the killer? I must have missed something.
His wife was one of the two dead women found in the cellar at the start of Thursday's episode. Having said that, it was still strange he took the other women back instead of taking her to safety.
On another point. When the DI & Jack went to Roper's flat, she unlocked the door by swiping her credit card down the door jam. I am pretty sure it was UPVC door that would have had a multi point mortice lock system which she would never open with a credit card. In addition, she swiped the credit card down part of the door where there is no lock. You could see the lock lower down. I doubt it's even possible to do that to a wooden door with a Yale lock it the manner she was supposed to have done it.
After she did it, Jack said "isn't that illegal?" What he should have said is "isn't that impossible?"