Frank Taggert is a character who makes a one-time appearance in the Season 2 episode titled "HX-1".
Frank Taggert is the father of Mace Taggert. When the HX-1 helicopter is stolen and Hawke is asked to find it, he studies the raid and sees that the thieves used a helicopter tactic which only his brother Saint John Hawke, Mace Taggert and Colonel Martin James Vidor employed. The latter two are dead. And so, Hawke thought, was Mace. In search of clues, Hawke goes and looks up Mace Taggert's parents.
With Mr. Frank Taggert and his wife, Hawke talks a little about the old times in Vietnam. They look at some old photos and Mrs. Taggert tells Hawke that they know every step Mace took during the last two weeks before he died. Hawke tells them about the HX-1 raid and how it used a tactic which only Saint-John or Mace could have pulled off.
Mrs. Taggert is instantly excited because there is a chance that her son is still alive. But Frank doesn't buy it. As far as he is concerned, Mace is dead, with an honorable grave in Arlington. He accuses Hawke of trying to imagine something to console himself. He could have saved St John and Mace during a mission in Vietnam but failed to do so. He angrily throws Hawke out of his house shouting after him: "You wanna know that you didn't let them die. Well, I am telling you that you did let them die! You let them die!"