***** S02E01 A Minority of One
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DI Frost investigates a
Seriesof commercial robberies assisted by newly promoted Criminal Investigation Department (CID) officer DC Carl Tanner (Lennie James), who is black. Superintended Mullett has promoted Tanner specifically to encourage diversity on the force as local racial tensions are increasing. When Frost makes an arrest, Mullett's only concern is that the culprit being black will further increase the risk of race riots. The white Natalie Bell, Frost's main informant on the significantly diverse Eastdean Estate, is killed when her apartment is set on fire, and Frost believes it was retaliation for her informing him about crimes on the estate by black residents. However, once the autopsy reveals she was beaten before the fire, Frost uncovers that Ritchie Gibbs, the father of Natalie's son, hit her in anger because of the violent people she allowed around his child, and set the fire in an attempt to destroy the evidence. Frost also realises that Natalie was exclusively telling him about and making up crimes by black people, out of spite against the black Gibbs's previous physical abuse. Meanwhile, the robberies are traced to violent white criminal, Paul Aspinall, who agrees to inform on the ringleader.
***** S02E02 Widows and Orphans
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DI Frost investigates a
Seriesof burglaries directed against old age pensioners, assisted by new female DS Maureen Lawson (Sally Dexter), eventually tying them to non-violent burglar Bernard Elliott. At the same time, things take a serious turn when an elderly woman is badly beaten, eventually dying from her injuries. A second elderly victim is soon found beaten to death, leading to suspicions that a serial killer may be responsible. Frost concludes that the second victim knew her attacker and let them in to her home, and learns from her neighbour that, Ronald Gould, a driver for the bus to her regular bingo game, had offered to replace the broken chain on her door. Frost confronts Gould at his grandmothers home, where she berates Gould for lying and insults his mother, who abandoned him as an infant, causing him to snap and almost bludgeon her. It is revealed that, as a child, Gould was diagnosed as obsessed with the approval of his elders, and despite his outward nice personality, he suffered violent outbursts when upset. Gould targeted his victims due to their age and attitudes, attacking them on and around 26 March, his mother's birthday. Frost is also able to link him to the murder of another elderly woman years earlier.

Meanwhile, Frost develops a romantic interest in his late wife's nurse, Shirley Fisher. He admits to her that he stopped talking to his affair partner, Eileen, before his wife died, out of guilt.

***** S02E03 Nothing to Hide
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DI Frost investigates the murder of a young, homeless drug addict, Ben Cornish. Frost works alongside DC Frank Costello (Neil Dudgeon), who was recently demoted and moved to Denton after punching his superior officer, who had taken over Costello's long-worked case at the last minute to receive the credit. Costello is eager to demonstrate his abilities and earn back his rank.

Cornish's autopsy reveals he was viciously beaten to near death before choking on his own vomit. Frost soon learns that Cornish had antagonised several people recently: he had stolen from his sister Anne and her husband Ray, again, blackmailed a local doctor for abusing Cornish as a child, and been forcefully evicted from an abandoned house he was squatting in, before threatening revenge. Though Frost's main suspect is the doctor, an offhand comment by a fellow officer reveals that he had arrested Ray for drunken disorder on the night of Cornish's death. Ray confesses that he had run into Cornish and intended to scare him for all the trouble he had caused himself and Anne, but went too far and killed him. Frost later meets with his former affair partner, Eileen, to apologise for suddenly ceasing all contact. She admits she truly loved him, but has since moved on due to the pain he caused her.

4 Stranger in the House
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DI Frost investigates a violent rapist who hides in the homes of his victims, mainly people whose jobs involve them wearing uniforms. He has left his many victims, and their families, traumatised, with one attempting suicide. WPC Hazel Wallace is assigned to support Frost on the case after the rapist unsuccessfully attacks a woman because her colleague at Staunton Towers saw him sneak into her car, and a 17-year-old girl, Alison Cook, goes missing and is presumed to have been abducted by the rapist because an unidentified man was seen in her home. Alison is returned home and it is revealed that she caught her mother having an affair in the home and ran away, and while her dad, Martin, falls under suspicion as he did housework for some of the victims, it is learned that he is impotent and aware of his wife's affair.

Frost realises that each victim lived near open areas such as forests, reducing their search area, and arranges a trap with Wallace to draw the rapist out, but Wallace panics when confronted by a masked man. Police trace the masked man to his home and learn he is Gordon Perryman, a night shift guard at Staunton Towers, who has been operating as a burglar. He reveals that he and his partner, Nick Daish, cover for each other so they can perform other tasks instead of working. Frost realises that Daish is the rapist, and learns that he was interested in Wallace. Believing she let the case down, Wallace returns home upset, where she is confronted by the rapist, but successfully incapacitates him just before Frost arrives to help. Unmasked, Daish gleefully admits he took pleasure in taking power away from the women.

Meanwhile, Frost invites Shirley Fisher to accompany him to a reunion event in London for all Victoria and George Cross holders, but, distracted by the case, he arrives too late to meet an irate Shirley at the train station, and she returns home.