There’s a growing feeling that perhaps Homeland has its best days behind it. After the thrill of its first season, and then the creeping implausibilities of the second, this third series could be pushing viewers’ limits. Surely former soldier and terrorist, Brody ( Damien Lewis) should be dead by now and Carrie on a long holiday in the sun where she can finally wipe away her tears? The first series had a sharp sting of believability, but so far this one is sinking into soapie territory. Tonight, Brody’s highstakes mission is jeopardised by his deteriorating physical condition and Quinn ( Rupert Friend) makes an awkward discovery about Carrie.