She is the assistant of Giles Bretwithe. Famous in Midsomer Morchard for her bitter, acid and nosy behaviour for which nobody likes her. Everyone, jokingly or not, wonders how Giles can stand her.
She's in love with her employer, but he could never reciprocate her feelings, being homosexual. She always refused to accept it, to the point that, when she accidentaly saw Giles making out with Sebastian Farquaharson, she started preventing the two to meet again, justifying herself by saying that this was for Giles' own good. Then she started blackmailing Sebastian for "what he tried to do to Mr. Bretwithe". Despite this, she reveals his "dirty little secret" to DCI Tom Barnaby without reserve.
When Gerald Farquaharson killed Giles Bretwhite and Frank Bishop to be able to keep the manor he lost in a bet, she tried to blackmail him through the document that legalized the bet, so he killed her too. According to Gerald, what she did wasn't made for money, but for revenge. For this, when he's arrested, he acknowledges that Iris, like himself and the other victims too, was quite worthless so not a big loss for society.