In April 2151, Klaang was hired by the Klingon High Council to obtain information that the Suliban Cabal were attempting to fuel a civil war between the Great Houses of the Klingon Empire. He used his K'toch-class scout to travel to Rigel X to meet with a Suliban agent named Sarin, who as a former agent of the Cabal had access to the Suliban plans. In order to safeguard the information, it was encoded into his DNA.
As Klaang left Rigel X to head back to Qo'noS, he discovered that he was being pursued by two Suliban agents. After diverting course, Klaang was forced to crashland near the town of Broken Bow, Oklahoma on Earth. Klaang was able to kill his pursuers by leading them into a grain silo and destroying it with his disruptor. However, Klaang was in turn shot by a local farmer named Richard Moore.
The injured Klaang was taken to Starfleet Medical in San Francisco, where he was treated by the Denobulan doctor, Phlox. Ambassador Soval recommended that Klaang be taken off life-support in order to keep in line with Klingon tradition. However, Admiral Maxwell Forrest and Captain Jonathan Archer wanted to return Klaang alive to Qo'noS using the newly-launched Enterprise.
Enroute to Qo'noS, Enterprise was boarded by the Suliban and Klaang was captured from sickbay and taken to a Suliban helix where he was interogated by Silik. Fortunately, Klaang was rescued from the helix by Captain Archer and Charles Tucker III using a stolen Suliban cell ship. He was later returned to Qo'noS and the Klingon Chancellor was able to view the data regarding the Suliban's actions in Klingon space. (ENT episode & novelization: Broken Bow)
Due to his life being saved by humans, Klaang was dishonored. He was sentenced to spend the rest of his life at Rura Penthe and Praxis, mentioned in the Report to Klingon High Council on Archer. (ST reference: Federation: The First 150 Years)