Senior Constable Ben Stewart
Ben arrived in Mt Thomas in the episode 'Victims', screened in mid 1998, as a Detective Acting Sergeant from the Organised Crime squad. 
Ben returned to Mt Thomas a few months later in the episode 'Nine Lives', but as a Senior Constable. However, after Maggie returned from the witness protection program in mid 1999 and resigned from her post as Acting Sergeant, Ben was promoted again.
Ben was separated from his wife, Rachel, and three children - Emma, Josh and Maddy - when he arrived in Mt Thomas and his divorce came through soon after.  Rachel came to town in 'Married to the Job' to tell Ben that the kids had called a family meeting and told her they wanted their parents to try again.  Ben wasn't so sure about this suggestion to start with but he eventually came around to the idea and he and Rachel spent the night together.  However, Rachel got cold feet the following morning and told Ben she had only come to see if things would be different - Ben was called out on the job and she pointed out that they wouldn't, he was still "married to the job".  She also told a devastated Ben that she was going to marry someone else.  In 'The Blame Game Part 1' Rachel told Ben that she's moving to Perth and that she's taking the kids with her.  Ben does his best to stop her, but to no avail.
Ben was always very attracted to Maggie, especially after she believed in him when he first arrived in town investigating the lost police guns.

Ben Stewart
To add to the problem, Maggie had kissed Ben when he left town the first time, so when Ben came back he thought he was in with a chance.  They did kiss again when they were both a bit drunk but Maggie backed off. Maggie  chose PJ over Ben when they became engaged at the end of 1999 .  Ben was devastated by Maggie's death - he loved her despite the fact that he knew they could never be more than friends.
Ben frantically began to study for his Sergeant's exams in mid 2000 to try to make the Sergeant's job officially his.  However, the arrival of Tess Gallagher put an end to his hopes.  Their initial meeting created sparks  but since Tess came to work in Mt Thomas and therefore, taking the job Ben was certain to get if not for her, things have been all but rosy.  Ben  will do anything to get out of working with her .  Ben doesn't like his new colleague's methods of policing but despite this he'll give her a chance, because of the type of guy he is.
In Season 9, Ben's past came back to haunt him.  In a very surprising back-story it turns out that he was briefly married to his childhood sweetheart, Angela, who comes to Mt Thomas to find him.  However, she has remarried and her husband follows her, not too happy that she and Ben seem to want to pick things up where they left off.