"I'm just trying to tie up loose ends," Tolin claimed during an interview with dead Karen's boss. Well, for goodness' sake, go on then! With only this and one more episode to go, things are still rather scattered, and Collision's got its work cut out if it hopes to cover everything in only one more hour.

So Karen's boss got a new PA to start work before he even knew that Karen was dead. Hmmm (*rubs chin*)... interesting. The dodgy guy Karen thought was a Guardian journalist was actually an impersonator of a Guardian journalist. Hmmm (*rubs chin again*)...curiouser and curiouser. Over on the other side of town, Tolin's confiscated Sidney the freelance piano teacher's computer, suspecting him of unsavoury behaviour. Hmmm...

Assuming you have time for this many ‘Hmmm' moments - I certainly don't - then all this was vaguely interesting. None of it made adequate use, though, of the character of Tolin, who spent all this action marching about stiffly, not reacting at all, apart from an odd, inappropriately gleeful grin at the prospect of catching a paedophile who's already dead.

He came into his own, very much, in the suddenly very dramatic moment outside his house when the recently released Harry Campbell came to pay a visit. It was a massive showdown, actually, and revealed - but we'd already guessed, right? -  that Mrs Tolin was killed in a car crash that also put Jodie Tolin in a wheelchair, Harry Campbell being the drunk-driver who caused it and went to jail.

Tolin's eyes grew larger and more watery than ever as Campbell craved a conversation with him to assuage his guilt. "You crippled my daughter. You killed my wife. I can't forgive you," spat Tolin to a greasy, squirming Campbell. "I read the Bible while I was inside. I forgive you for your hatred," returned Campbell. The notion of Campbell being in a position to forgive anyone sent Tolin into a blind, violent rage. This was all good stuff that reminded me of the class that I knew was in the writing but had been barely demonstrated over the last couple of nights.

Sadly, the careful writing did not make an appearance in the scene between the tiresome, limp Jane and the nauseatingly clichéd Richard. At the art gallery, Jane felt all silly and uncultured and in awe of the paintings, only to be told by Richard that he owned a couple of them, and, by the way, did she fancy going away with him on some impossibly luxurious trip?

All this slush aside, the actual mechanics of the scene were flawed. When Jane arrived at the gallery, she took a glass of champagne from a tray, then took one sip, then swapped the glass for a brand new one, saying a wry comment to the bloke next to her about having had a long day. That's just stupid writing. Then later, Richard said to her, "I want to buy you lunch," as if it was lunch time, when it was obviously an evening art opening and we'd heard Jane say the thing about "long day" earlier in the scene. That kind of clunky writing is just unforgivable.

Gosh. That's all I can say. Gosh. At the start of all this I said it was a shame it felt like a "long haul" to sign up to one of these five-nighters. But if this scheduling is going to work in future, it has to be up to the writing to make it feel effortless. At this stage in Collision, I feel owed an awful lot of drama and exposition in order to be able to take away anything from the week. Well, tomorrow's final episode better be good.

Read our review of episode three here.