The body of Richard Seager a former Biochemist, is found under a Jaguar Mark 2. The day before, the victim had been collected from prison by his wife, Martha Seager after serving a year for causing death by dangerous driving. Before his death, Seager managed to scratch the number ‘500’ into the car’s paintwork.

The episode was rated 7.98 from 94 votes.

When a student is found dead during a college-based clinical trial for a new anti-depressant, Lewis and Hathaway struggle to determine whether the incident was murder or suicide, and receive little assistance from the institution's evasive psychiatric professor. A second student's death then leads to the revelation that the trial's participants are all operating under the influence of mind-altering drug ketamine, and that the lines between love, obsession and madness have become dangerously blurred.

The episode was rated 7.99 from 82 votes.

A female bishop visiting St Gerard's College is found dead after drinking poisoned wine, and when another two killings occur, both mirroring macabre murders from Jacobean revenge tragedy, it appears the culprit is targeting candidates in the election to become vice-regent. However, when Innocent learns one of the suspects is hiding a dark secret, Lewis and Hathaway realise the motive is much more twisted.

The episode was rated 7.99 from 90 votes.

Lewis and Hobson are examining the body of murdered Vicki Walmsley when a theft of etorphine is reported by the Garsington Equine Centre. The drug was last used a year earlier on a horse that injured its teenage rider, Joshua Grace – the brother-in-law of Reuben Beatty, the first murder victim.

The episode was rated 8.00 from 85 votes.

It soon becomes obvious that the case has everything to do with Alastair’s failure to save the life of a badly hurt teenager, Nabeel Sira, during surgery. The hospital staff have closed ranks and the boy’s parents are considering their options. A second murder then happens.

The episode was rated 8.01 from 88 votes.

When botanist Li Nash digs up the body of recently buried English Professor, Murray Hawes, Lewis and Hathaway find themselves involved in an impossible quest. Murray was a man who was possessed with solving the riddle of Lewis Carroll's "The Hunting of the Snark". They soon find out that Murray had a rivalry with his brother, who is a lecturer in Theology and Moral Philosophy. They also have to deal with interference from Michelle Marber who is an amateur detective, who believes that that the killer is local medical researcher Alex Falconer.

The episode was rated 8.02 from 90 votes.

All is not what it seems between two married couples who are old friends, as Lewis and Hathaway start to discover when one wife is found hanged.

The episode was rated 8.04 from 76 votes.

Lewis, Hathaway and Hobson look around the new crime scene as Carl Drew, Stella Drew, Martha Seager, Adam Tibbit, Graham Yardley and Adam’s girlfriend Rachel Cliff wait anxiously. The body is revealed to be that of Soo-Min Chong, a Korean student who vanished 15 years ago. Seager was the last person to see her alive, Carl Drew was her boyfriend, and she was Martha’s organ scholar at the chapel. Hathaway is later shocked to discover Adam’s body at the school, with a simple suicide note. Carl, Adam’s former teacher believes that he must have pushed the boy too hard. Forensics end up revealing a close relative of Adam’s had been in Seager’s car. After Martha is found stabbed to death, Lewis and Hathaway start to close in on the killer who is becoming more desperate to cover their tracks.

The episode was rated 8.06 from 79 votes.

After a difficult start, Lewis and Hathaway's partnership seems to have gained some semblance of normality. DS Maddox has become a part of the team. Her abilities will be put to the test when an investigation begins on the brutal murder of an American classics student Rose Anderson Her body is hauled from the canal with a stand wound to the neck and abdomen. Suspicious soon fall on astrophysics professor, Felix Garwood who had recently broken off an affair with Rose. However, Felix was married to Rose's supervisor, Philippa Garwood. Could the jealous wife have committed such a murder?

The episode was rated 8.06 from 94 votes.

Hathaway and Maddox continue to investigate the murder of Travis as the trail leads back to Lewis’s original case. The two detectives attempt to prevent another murder and Lewis sees himself isolated and alone with his reputation in jeopardy.

The episode was rated 8.09 from 100 votes.

Lewis' reputation is jeopardized when the very first case that he solved as a DI is reopened for appeal and new murders are committed with the original weapon.

The episode was rated 8.10 from 111 votes.

Lewis and Hathaway are drawn into a world of virtual bullying, but very real murder, when Professor Miranda Thornton is found dead after her dating video is leaked onto a vicious website. Miranda's death initially looks like suicide but, as the detectives dig deeper, they realise that it is actually the final revenge of an old enemy.

The episode was rated 8.11 from 85 votes.

Oxford's last all-female college is holding a reunion party to say goodbye to one of its most popular professors. After a guest is found murdered, Lewis believes the killing is connected to an attack that happened at the same building 10 years ago. He turns to his former DS, Alison McLennan, to help him with the case but it ends up taking a new twist after two more bodies turn up.

The episode was rated 8.12 from 91 votes.

With his six-month trip to New Zealand with Hobson on the horizon, Lewis is in a race against time to save not just his career but his relationship too.

The episode was rated 8.13 from 122 votes.

Liam Jay is in intensive care and Lewis and Alex believe that he has information about the death of Matt Whiby and the mysterious cremation. It is revealed by Emma Barnes that Johnny Jay, Liam’s father, was at the fateful supper party and he is missing as well.

The episode was rated 8.15 from 73 votes.