This is set when Karen was knocked down in series 3, episode 6, only in this version, she isn't ok.

...

He hurried back into the house, keen to escape to cold breeze. The car alarm's insistent wailing had proved irksome enough for his frustration to build until; finally, he kicked it, purely to vent his feelings. Surprisingly enough, it had shut the car up, but it had also succeeded in causing his foot to throb and ache, which only added to the bloody-minded state he had been in since his dispute with Sue. He fiercely regretted the kiss. He had done as soon as he realised what had happened. It was beyond his comprehension how he could throw away a relationship like his and Sue's and he was desperate to put it right, but the discovery of her husband's latest exploit continued to smart and she was having none of his efforts to atone for his misdeed.

He had a lot on his mind and was surprised to be jolted back to reality by a mildly frantic looking Jake, appearing, as if from nowhere, onto Pete's horizon.

'There you are-look, Dad, that was Mum on the phone and she says you've got to keep calm'

'Keep calm?' His son's words had left him confused and a little bewildered.

'She said "Tell Dad to keep calm and not to panic 'cause everything's going to be ok"'

'If everything's going to be ok, why do I need to keep calm?' he demanded, trying a logical approach now, in an attempt to decipher his son's garbled instructions from his mother.

Jake played with his jaw for a moment, before confessing to his father, 'Karen's been knocked down'.

Pete's eyes widened, as an overwhelming panic began to wash over him, mixed with a tinge of hopeful, yet hopeless disbelief. His brow furrowed and suddenly, the world seemed a crueller place. How could his only, precious daughter have been knocked down? He heard about these things all the time in the news, and had given his children the appropriate the advice, or so he thought, to avoid this fate for themselves. He had been so wrapped up in his own affairs this evening, he had paid little attention to his young daughter, so nervous about her role in a school concert that she could easily have failed to remember road safety. HIS daughter-HIS Karen! He imagined her tiny body crushed by the weight of a speeding car-no, a truck. He berated himself over and over for not paying her more attention, forgetting how much he cared for her, forgetting to appreciate her existence and for not spending enough time with her. He had no rational answers, his mind was still coming to terms with the information and could only force out,

'Oh my God! Wha-', before Jake cut him off.

'No, Dad, it's ok, Dad-Karen will be ok, seriously. Mum's at the hosp-'

'Karen 'will be ok'? Jake, what's happened to Karen? What did Mum say?' he asked urgently.

Jake was silent for a long moment, apprehensive about admitting Karen's injuries to his already agitated father. He tried his best to make them sound as trivial as possible.

'Well…she'll be ok, remember' he reminded his father before rushing on, conscious he was about to be interrupted once more, 'because broken legs heal in, like, two months, don't they?...and they gave her transfusions to replace the blood she lost, so that's okay now…but', he was scared to carry on, too aware of his father's bone white face and mask of silent horror. He rushed the last part, 'the only thing is, they won't know about head or back injuries properly until she's awake', he was seriously worried about his father now, who looked to be on the verge of breakdown. He finished with a murmured, '…which might not be for a few days.' He gave his father some moments to digest the news, before pointing out, 'Mum's at the hospital with her now-and, you can't ring her, because she's not allowed to use her phone in the hospital-but she says "everything's ok, don't worry, stay calm" and she'll give us a ring in a bit'. He was beginning to wonder whether he should help his father sit down, his face still dumbfounded and having not said anything for several minutes, when Pete managed a stammering,

'yeah, but she-but she's been…'