Uh-oh, beware. It's the shadow of the 'absent MP'.
It's one of the best tactics in the PMQs book.
The absent MP is usually a figure that the prime minister or a member of his cabinet is at odds with – their empty seat in the chamber a reminder of the continuing rift.
This week, Jesse Norman was said 'absent MP'.
A "big thinker", who pondered David Cameron's big society at length, Norman led the backbench revolt over House of Lords reform.
Apparently, he had a big, old barmy with the PM last night, when Cameron decided to publicly dress him down – and the whips asked him to leave the estate (supposedly).
Of course, Ed Miliband could not miss the opportunity to deploy the 'absent MP' jibe – and to great effect.
Whisper it, but the Labour leader was pretty good today.
His opening line was a cracker. When asked why he wanted to be prime minister before the last election, "with characteristic humility [the PM replied]: 'Because I thought I'd be good at it.' Where did it all go wrong?"
Even Andrew Mitchell – flanking the PM's left – twitched mouse-like with amusement at that one.
Cameron responded with a series of lists – always a bad sign. "It is this government that has capped immigration, increased spending on the NHS…"
Pointing at Miliband, he added: "I can't read out the list of all the things he got wrong."
(Bet he wished he could. It would have avoided what came next.)
"We understand it was fisticuffs in the lobby last night," said the Labour leader, with a barely-suppressed smile.
"The posh boys must have ordered him [Jesse Norman] off the estate today because he doesn't seem to be here."
It was an excellent use of the 'absent MP' ploy (only slightly undermined by the fact that Norman is not in the chamber because he's visiting the Queen in Herefordshire. That probably out-poshes the 'posh boys' on the frontbench.)
"Tittle-tattle and rumour," said Cameron, waving away the accusation with his hand. "How pathetic."
Labour were "determined to vote yes and then vote no", he said of the Lords reform vote. "How utterly pathetic."
But Miliband was on a roll. "The government is a shambles and he blames the opposition," he said. "The problems started months ago with the part-time chancellor's Budget."
Turning to the economy, Miliband shouted above the din: "We've got to do more to bring the economy back to health. [We've got] a double-dip recession made in Downing Street."
Cameron sounded more Gordon Brown than Tony Blair as he launched into another list. "Unemployment is down, interest rates are at a record low," he said.
"We are net exporter of cars for the first time since 1976. We've started the next project which is Crossrail… This country will never forgive them for what they did," he finished, pointing at the Labour benches.
"The redder he gets, the less he convinces people," said Miliband, deploying a tone of fake disappointment usually reserved for primary school amateur dramatics.
"It's the same lecture that we've had on the economy for the last two years. Things are getting worse not better."
Of course, Cameron was entitled to the last word. "There's only one person who's red around here: that's Red Ed."
Oh, that's a vintage PMQs line. Ed hasn't been called 'red' for a few months now. He can thank recent interventions from the PCS and Unite for that one.
But Ed wasn't the only one accused of blushing rouge.
Conservative MP Anne-Marie Morris stood bravely to defend the government, arm in a cast.
So loudly did she shriek, and so wildly did she fling around her supposedly injured arm, that the House was in fits of giggles by the time she finished.
The frequency of her high-pitched squeaking was so extraordinary that I'm almost certain the 'absent MP' will have heard it in Herefordshire.
Expect the Queen's corgis to come running.
(They're better trained than some of Cameron's backbenchers...)