Who was the old man?

[Morthoron]

Originally Posted by Mansun

If Theoden was poisoned, it could have killed him given his age. And how did Gandalf manage to wear off the poison by his appearance alone in the Golden Hall? Whatever you are ascertaining above, give more detail please. Quote the full text from the source.

I will indeed supply you with the text (although I've seen neither hide nor hair of any textual proof I asked you to submit regarding Theoden being 'bewitched' by Saruman's spirit):

Originally Posted by Unfinished Tales, Chapter V The Battles of the Fords of Isen

...But it [Theoden's malady] may well have been induced or increased by subtle poisons, administered by Grima. In any case, Theoden's sense of weakness and dependence on Grima was largely due to the cunning and skill of this evil counsellor's suggestions.

Originally Posted by LotR, 'King of the Golden Hall'

'If this is bewitchment,' said Theoden, 'it seems to me more wholesome than your whisperings. Your leechcraft ere long would have me walking on all fours like a beast.'

As you can see, there is never a direct reference to Saruman regarding Theoden's stuppor (drowsiness, a sure sign one is drugged), and Grima is held responsible for the prolonged and addled dependence of Theoden. In addition, Theoden himself uses the word 'leechcraft', which by definition refers to archaic medicinal practices. In an analogical sense 'honey in the ear' is whispered lies as well as a non-invasive method of introducing poison into the body.