The egg in the fridge was a cunning egg. Indeed, that was the sole reason Lionel had chosen it in the first, or, indeed, the last, place.
It had locked itself inside the egg box. But though cunning, it was also stupid. Well, it was only an egg,after all, and didn't have one brain cell, never mind two, to rub together. It hadn't reckoned on the possibility that, having locked the inside of the egg box, it could a) still be opened from the outside and b) taken out of Lionel's fridge, egg box and all, by an even more cunning thief.
The even more cunning thief in question was a woman. She lived next door to Lionel and often sneaked in in the dead of night, or the alive of morning, or the moribund of the late evening, to steal food from Lionel's fridge or cupboards.
Had he smelt her breath, he would have detected the faint but unmistakeable scent of Marmite (other yeast extract based products are available) which would have alerted him the the possibilty that she might be the person responsible for the gradual disappearance of his secret stash of night-time twiglets. She was also indirectly responsible, therefore, for his current predicament.
This woman's name was Eliza. While she snuck out of Lionel's kitchen, blissfully unaware that his digits were being feasted on by Rancid the hound, she thought ahead to the delicious twiglet omelette she was planning on having for her breakfast, and thought how useful it was to have a neighbour who so considerately left his back door unlocked all the time, saving her the trouble of going to the shop and having to pay for food, especially as her purse had gone missing two years ago and she couldn't be bothered to search for it.
She opened her own back door,and was dismayed to find her own fridge door standing open. She quickly surveyed the contents - which weren't there.
''Oh dearie me'' said Eliza. ''No butter, no omelette.'' She sank to the floor, sobbing hysterically. She was so deep in misery that she did not notice a figure sneaking into her kitchen, picking up the box containing the cunning egg, and sneaking out again.