Sam Knight is a non-canonical character created for the 2003 ITV adaptation of the novel Sparkling Cyanide. He is the grandson of Col Geoffrey Reece and his wife Dr Catherine Kendall. During the course of the show, his house is under renovation and he and his mother Rebecca Knight have moved into the house of the Reeces.
Sam plays an important part in the breakthrough which leads to the solving of the case. Sam had left his toy robot on the table where Catherine was about to serve tea. Sam had asked for 3 lumps of sugar in his, while Rebecca wanted no sugar. Sam's toy robot fell to the floor and Reece picked it up but put it on the table against a different seat. Rebecca put Sam's cup next to his robot. But this is Catherine's seat. When she drinks her tea and it tastes incredibly sweet, she and Reece suddenly realise what happened. They think back to the scene at the night club where Iris Marle's evening bag had fallen onto the floor. A waiter had picked it up and put it at a random position--next to George Barton's cup. George drank the champagne and died but actually Iris was the intended victim. In this adaptation, the guests return to their same seats after the dance. It is the poisoner who gets mislead and, taking the cue from the evening bag, puts the poison into the wrong glass. In the original, the guests return to the table after the dance and sit down, taking their cue from Iris who sits by her hand, which is now one position over.
Sam Knight is portrayed by Joseph Scatley (credited as Joseph Scattley).