You should watch:

Allegiance

This was episode number 18 of season 3.

The following characters appeared in this episode:

Alien #2

Alien #1

Captain Jean-Luc Picard

Counselor Deanna Troi

Commander Wiliam T Riker

Doctor Beverly Crusher

Esoqq

Kova Tholl

Lieutenant Worf

Lt Commander Data

Lt Commander Geordi La Forge

Mitena Haro

Wesley Crusher