Series 4

01 Theory Episode 112th September 1968 The No. 11 District squad has just completed a rearrangement of their Headquarters accommodation, taking over the house next door to provide extra space; and to bring Gilbert and Barlow into closer proximity with Watt and his team. 02 Proof Episode 219th September 1968 03 Bird Of Passage Episode 326th September 1968 04 See The Rabbit Episode 43rd October 1968 05 Take Them In Singles Episode 510th October 1968 06 Red Herring Episode 617th October 1968 07 Five Pairs O' Hands Episode 724th October 1968 08 Minor Incident Episode 831st October 1968 09 An Old Song Episode 97th November 1968 10 Big Boats, Little Boats Episode 1014th November 1968 11 For A Rainy Day Episode 1121st November 1968 12 Assistance Episode 1228th November 1968 13 Equal Status Episode 135th December 1968 14 Obstruction Episode 1412th December 1968 15 Going Quietly Episode 1519th December 1968 16 On Christmas Day In The Morning Episode 1627th December 1968 17 Departure Episode 172nd January 1969 18 Cross Reference Episode 189th January 1969 19 Run For The Hills Episode 1916th January 1969 20 Pressure Episode 2023rd January 1969 21 A Quantity Of Gelignite Episode 2130th January 1969 22 Critical Path Episode 226th February 1969 23 Persistence Episode 2313th February 1969 24 Second Chance Episode 2420th February 1969 25 How's The Wife Then ? Episode 2527th February 1969 26 Right To Search Episode 266th March 1969 27 Proved Connection Episode 2713th March 1969