I think I may need a read through some old threads as I appear to have missed a series or two
Last series started off with a body in the trunk, the little brother having filmed nasty bloke on his phone.IIRC they went abroad to follow someone <insert laughing smilie because my memory is so bad>
Yes you've missed a series, the one you're describing is series 2. Series 3 involves the hunt for a serial killer.
I'd either hunt around for the old threads, or, look at the Guardian tv section, they started doing week by week blogs from series 3.