I hadn't realised that the series was filmed over a number of years and had assumed it was a single season. This seems to be reflected in the progression of the lives of the characters who have children, move house, change work as in any real life.
There's an overarching theme throughout, Anne's past as a Stasi agent who left the organisation leading to dire personal consequences. She draws on her contacts from those times to obtain evidence or clues on how to solve cases. At the same time, she is working on her personal project about her son and his life.
She and Youssef make an odd couple but an effective one in their investigations, helped by (or hindered sometimes) by Kommissar Ralf Eisner who always seems to be allocated to the cases they are working on. OK, a bit of poetic licence by the scriptwriters.
With help from relatives and friends, the cases are resolved in the end, although not without a couple of extra murders or even suicides on the way. Intertwined in them are the personal themes mentioned above.
I'm puzzled as to the translation of the name of the series into English. "Die Füchsin" translates into English as "The Vixen". That's a perfectly acceptable title.
All in all a worthwhile watch. Episodes are ninety minutes long, so it's necessary to settle down and relax.