段五郎接到了研究所所长小岛博士的紧急电话，告知他收到了一条威胁性质的电话，要求交出一份绝密文件，不然就要他的命。小岛博士陷入了困境，只好求助于段五郎，请他在晚上8点钟来到他的家中详谈此事。

当夜晚8时分，段五郎准时赶到了小岛家的门前，但按响门铃后，却发现房门未被开启。他注意到房间内灯光依旧亮着，便无意中试探地转动了把手，惊讶地发现房门竟然是敞开的。 Segment Five immediately entered the house, only to find Dr. Isola lying unconscious on the sofa, with a handkerchief emitting a medicinal smell nearby.

At this point, Dr. Isola slowly opened his hazy eyes and instinctively felt his pockets, letting out an exclamation of despair: "It's gone! The secret file has been stolen!" Segment Five quickly asked who was responsible for the theft and when it occurred. Dr. Isola looked at his watch and replied that he had been watching TV while eating an apple about 30 minutes earlier; hearing the doorbell ring, he thought it was probably Segment Five arriving but found himself confronted by two men wielding guns instead.

The men demanded to know where the secret file was kept; Dr. Isola pretended not to know anything about it, after which they used a handkerchief to gag him and render him unconscious before disappearing into thin air.

Sure enough, there was half-eaten apple near the TV set with its power turned off. Segment Five picked up the apple from under the television and gave it a quick glance before saying dryly: "Dr. Isola is selling you out!"

Dr. Isola looked taken aback by this accusation but denied any involvement in such actions with feigned innocence until he realized that segment five knew something more than just what appeared on surface level as segment five threw down something in front of him.

Segment Five revealed how he unraveled Dr.Isloa's deception using nothing other than an ordinary apple.

He explained that apples contain oxygen-phenolase which is normally confined within cell walls without coming into contact with atmospheric oxygen unless cell walls are ruptured through biting or crushing causing them to turn brown due to oxidation reaction between oxygen-phenolase & O2 . Given that no color change had occurred in this particular apple despite being claimed as having been bitten by someone 30 minutes ago ,the likelihood of segment five believing such claim seemed highly improbable .

Thus ,by employing deductive reasoning based solely upon observation of physical evidence (apple),segment five exposed dr.isloa’s cunning plan as part of larger scheme involving forgery & extortion

Finally revealing hidden package filled with large sums of cash concealed inside refrigerator meant for paying off these thugs

In conclusion ,Segment Five proved capable not only solving crimes efficiently but also doing so without resorting brute force or violence

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