4x1 - Theory

September 12, 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.

4x2 - Proof

September 19, 1968

4x3 - Bird Of Passage

September 26, 1968

4x4 - See The Rabbit

October 3, 1968

4x5 - Take Them In Singles

October 10, 1968

4x6 - Red Herring

October 17, 1968

4x7 - Five Pairs O' Hands

October 24, 1968

4x8 - Minor Incident

October 31, 1968

4x9 - An Old Song

November 7, 1968

4x10 - Big Boats, Little Boats

November 14, 1968

4x11 - For A Rainy Day

November 21, 1968

4x12 - Assistance

November 28, 1968

4x13 - Equal Status

December 5, 1968

4x14 - Obstruction

December 12, 1968

4x15 - Going Quietly

December 19, 1968

4x16 - On Christmas Day In The Morning

December 27, 1968

4x17 - Departure

January 2, 1969

4x18 - Cross Reference

January 9, 1969

4x20 - Pressure

January 23, 1969

4x21 - A Quantity Of Gelignite

January 30, 1969

4x22 - Critical Path

February 6, 1969

4x23 - Persistence

February 13, 1969

4x24 - Second Chance

February 20, 1969

4x25 - How's The Wife Then ?

February 27, 1969

4x26 - Right To Search

March 6, 1969

4x27 - Proved Connection

March 13, 1969