Previous appearances on the S&BCC blog:
Here and here.
Episode under consideration today:
Games (Series 4)
Blah Blah ... Feldan crystals ... Blah Blah ... source of unlimited energy ... Blah Blah ... steal them from the Federation.
A computer called Gambit.
A scientist called Belkov who likes to play a chess-like game against his computer.
2:23 to 3:01
4:49 to 5:19
6:36 to 6:54
More chess related video clips available here.