In the Pale Moonlight:
Stardate 4607.6. Kirk decides that it is time to gain a new ally against the Romulans-- the Orion Syndicate. Harry Mudd, currently in the brig, suggests fabricating evidence that the Romulans were planning an attack on Orion and to present it to Syndicate high ranking boss Vreenak. Vreenak arrives, and Kirk shows her a record tape of a meeting of Romulan senators discussing plans to invade Orion. The charade fails when, upon an examination of the record tape, Vreenak recognizes that it is faked and takes off in her interceptor. However, the interceptor explodes, killing Vreenak and destroying the evidence. Harry has placed a bomb on the interceptor, thereby getting the Orions to declare war on the Romulan Empire and leaving one Starfleet officer with a very bad conscience.
(Summary based on synopsis by Bernd Schneider)