He comes into contact with John's son Lieutenant Commander Steve Mc Garrett, then still on active duty, who returns home to Hawaii seeking revenge and intending to take over the investigation into the murder of his father.
Danny's pistol is an H&K P30 although he carried a SIG Sauer SP2009 in the pilot.
He transferred from Newark PD to the Honolulu PD to be closer to Grace.
In the Pilot, Danny had moved to Hawaii six months ago and was a "greener than grass" homicide detective with the HPD when he was assigned the murder investigation of John Mc Garrett.
Full cast of Hawaii Five-0 season 8 from left to right: Jorge Garcia as Special Consultant Jerry Ortega, Chi Mc Bride as Captain Lou Grover, Beulah Koale as Officer Junior Reigns, Meghan Rath as Officer Tani Rey, Scott Caan as Detective Danny Williams, Alex O'Loughlin as Lieutenant Commander Steve Mc Garrett, Ian Anthony Dale as Adam Nishomuri, Kimee Balmilero as Medical Examiner Dr.
Noelani Cunha, Dennis Chun as Sergeant Duke Lukela, and Taylor Wily as Kamekona Tupola Detective Sergeant Daniel "Danny" "Danno" James Williams is a member of the Five-0 Task Force and the de facto second in command.