There was a time when NCIS fans thought Abby Scuito was dead.
As a fan favourite, you can imagine the palpable sense of relief when she pulled through – and actually went on to 'persuade' Robert King (Peter Jason) to confess that it was him that had organised a hit on her.
But no sooner was she back in the thick of things, when she decided to fly to London for good where she would oversee the charity her recently deceased partner, Clayton, had been planning to start to honour his late mother.
But now, some fans of the show are calling for her to come back – but gone rogue.
This would be a major change of course for a character who had a few ups and downs but was a nice person who has a genuine connection with her NCIS colleagues. Even more so, when you consider her reason for moving to the UK and how that would have given her such purpose in life.
That's not to say it couldn't happen, just that there would need to be a pretty major life-changing event to cause such a massive turnaround.
You might argue that the death of Clayton could be the catalyst for such a change. Especially given that she would no doubt feel an element of guilt about how and why he died.
However, it might make more sense for Ellie Bishop to go rogue and return as a terrorist. Ellie's personality changed noticeably following a series of traumatic events that included the breakdown of her marriage and the deaths of close friend Clayton and partner Qasim.
Indeed, such was her quest for vengeance following the killing of Qasim by Chen, that she (allegedly) contacted the Syrians to give up Chen who was now working for the CIA. Maybe she didn't really make that call. But the seeds of going rogue were certainly there with Ellie far more than they were with Abby.
There's no doubt that Abby turning her back on the good guys and coming back as a terrorist would be the bigger shock. But you get the feeling that it would also feel a little more forced. Of course, played in the right way by Pauley Perrette, and with powerful storylines, viewers may well get over the unlikeliness of a rogue reappearance by a fan favourite. But it's a big call for the writers who would be giving themselves a massive hill to climb in terms of pitching it just right.