Liquid City is the 1628th episode of The Bill.
While at a police function on the Thames with Supt. Chandler and D.C. Spears, D.I. Cullen spots a man climbing through the window of a riverside house. Cullen calls Sun Hill, but the rather inept team of P.C. Hollis and P.C. Taviner fails to capture the intruder. Embarrassed by the spectacle, Chandler assigns Spears to work on Sun Hill's burglary statistics, and she finds a link between a number of other break-ins. Chandler is furious when Cullen hires a criminal profiler, Roy Stenning, but his information gets CID close to a likely suspect. Rumours about the relationship between Spears and Chandler are rife throughout the station, and Spears is not popular with her colleagues, who accuse her of sleeping her way to the top. When P.C. Hollis is caught by Chandler for unauthorised use of the PNC, P.C. Taviner threatens to reveal a secret from their past at Hendon, but finds his own use of the PNC under scrutiny. Chandler and Spears meet for dinner, but Chandler is hesitant to move too fast. The intruder strikes again, this time setting a house alight, killing two children. With only D.C. Webb willing to help her, Spears tracks down the drifter responsible, Charlie McGann, whose family was killed in a fire in Glasgow, and who wrecks or torches houses out of jealousy.
When looking for Helen, Des Taviner says that he's looking for Miss Helen Feelan. According to the credits, Helen's surname is Chung. Helen Feelan is a different character who appears in the next two episodes, A Pound of Flesh and Home Run.