Poirot and Hastings have just left Mr Hardman's house.
‘See you, my friend,’ said Poirot to me, as we left the house together, ‘he has one law for the titled, and another law for the plain, this Mr Hardman. Me, I have not yet been ennobled, so I am on the side of the plain. I have sympathy for this young man. The whole thing was a little curious, was it not? There was Hardman suspecting Lady Runcorn; there was I, suspecting the Countess and Johnston; and all the time, the obscure Mr Parker was our man.’
Why does Poirot say 'see you' instead of 'you see'? It seems he's talking to Hastings, meaning 'you know, you understand', and not saying goodbye to Hardman.