Warning: contains spoilers forShetlandseries nine episode three.Billy, get me everything you can on this new marine lab, requested DI Calder in episode three. Copy us in too, Billy, because that shady facility is shaping up to be the epicentre of this years investigation.Just what is pluripotency expert (thank you, freeze-frame) Dr Mohan doing in that remote laboratory? Genetically engineering a new species of cold-resistant detectives to replace our shivering duo? Splicing frog and dinosaur DNA to turn Shetland into a new Jurassic Park? Perfecting the recipe for the ultimate shortbread biscuit?Whatever Mohan is up to, its part of series nines heightened twist onShetlands usual investigations. Spies, secret experiments,X-Files-style cold opens in which Looney-Tunes locals have their brains turned into mashed potato after getting caught trespassing in the no-go zone its a long way from this crime dramas usual fare. Unless the lab turns out to be a red herring distracting us from a more domestic answer to the question of who killed Annie and Anton,Shetlandis venturing onto new ground.And so is DI Calder, whos formed an unexpected to her, at least attachment to little Noah Bett. Ruths awkward interactions with Noah are rather sweet to watch, like eavesdropping on a shy kid trying to make a new pal. Contrasted with Toshs calm, capable, adult approach to the boy, Ruth comes across more like his peer than an investigating officer. The bond shes slowly building with Noah may prove vital if he remains the only witness to the murders.That fact hasnt escaped Professor Rossi, the former Oxford spy apologies,analyst who appears to be running his own investigation into Annies murder. Rossi has repeatedly asked after Noah, and this week parked outside his aunts house to spy on his police visit. If the previous series hadnt revolved around a genealogy twist, we might assume that Rossi is Noahs biological father, butShetlandwouldnt repeat itself so soon. Rossis interest in the boy must be down to his status as a witness. Does Rossi suspect Noah, does he want to know what Noah saw, or does he want to ensure that he keeps quiet?Read more In short: is the professor to be trusted? At the halfway point of a six-part murder mystery, its traditional for everybody in the cast to look a bit sus, and Rossis sneaking around this episode and turning up unexpectedly at Ruths home (nice, the little nod to her continuing grief over Cal in that record collection chat), certainly fulfilled that requirement. He wasnt the only one dinging alarm bells. Debtor Patrick Harris and his creditor JJ Huang were clearly involved in some scheme that went awry on the night of the murders.There could be one more of those to add to the list, depending on whether Patricks younger brother Fergus pulls through after that cliffhanger argument on the boat. The Harris family are already a tragic bunch, and John accidentally killing his youngest only adds more pain. Poor Fergus was the sweetest of that already-sorry lot.Back to the suspects: Frank also looked decidedly green when Tosh mentioned having found Annies husband Ian at the seedy Mission during that awkward night out on fizzy water and dirty looks at the pub. Hes hiding something. As are the wealthy Jakobsons in their magazine-spread home and expensive knitwear. Astrid Jakobsons phone call to Anton on the night he died was almost certainlynotabout the finer points of the US high school movie genre.Clueless? Not quite. Tosh and Ruth have plenty to go on, but there are currently too many potential directions for a clear way forward to have emerged which, at the midway point, is exactly where things should be.Shetland series nine continues on Wednesday November 27 on BBC One and iPlayer.