She and Hannah grew up together at the same halfway house and grew close. One day she witnessed Hannah feeding rat poison to her counselor, effectively killing him. She once told Hannah's father Clint McKay who planned on using this information to get rich in the future.
Her name is later given to the police by Clint McKay and Lieutenant Debra Morgan goes to question her about the murder. Arlene is reluctant to give her information about the murder but Debra threatens to take her kids away and is forced to consider the offer. She visits Hannah McKay and tells her about the offer and Hannah tells her not to worry and that she will take care of it. Later when Hannah is arrested for murder she and Hannah form a plan to help her escape. Arlene poisons her to distract the guards and when they get to the infirmary she escapes their custody.
Hannah McKay has send some of her money to Arlene to keep it safe. Hannah plans to take it and leave Miami to start a new life. However, Deputy Marshall Clayton, is looking for her after being contacted by Jacob Elway. Dexter decided to help Hannah by driving her to Arlene's house. Hannah appears to support Arlene sufficiently to keep youthcare away from her children and allowing her to live in a better place. Inside, Dexter spots Clayton outside walking to the front door. He instructs Hannah to hide and instructs Arlene to act like everything is normal. Clayton is surprised to see Dexter at Arlene's place and wonders where Arlene got the money from to pay the house she is living in. Dexter pretends he is helping Arlene after they bonded over Hannah when the latter went to prison but escaped later. Clayton leaves, despite still suspecting them to hide something.