The Incredible Shrinking Man

Scott Carey (Grant Williams) is a businessman who is on vacation with his wife Louise (Randy Stuart) on a boat off the California coast. When Louise goes below deck, a large, strange cloud on the horizon passes over the craft, leaving a reflective mist on Scott's bare skin. The couple are puzzled by the phenomenon, which disappears as quickly as it had shown up.
However, one morning six months later, Scott, who is 6Â ft 1Â in (1.85Â m) tall and 190 pounds (86Â kg), notices that his shirt and slacks seem to be too big, but blames it on the laundry service. As this trend continues, he believes he is shrinking and sees his physician, Dr. Bramson (William Schallert), who reassures him that he is in perfect health and that "people just don't get shorter." Louise also dismisses his fears as silly, stating that he has simply been losing weight, but he continues to lose height and weight. His wedding ring falls off his finger. Louise becomes concerned when Scott points out that she no longer needs to stand on tiptoe to kiss him.
Finally, there is x-ray proof that Scott is getting smaller. His doctor refers him to the prominent laboratory, the California Medical Research Institute, and after nearly three weeks of sophisticated tests, Scott and his team of new doctors learn that the mist to which he was exposed was radioactive. This, combined with an accidental exposure to a large amount of common insecticide four months later, has set off a chain reaction that has rearranged Scott's molecular structure, causing his cells to shrink.
Scott continues to shrink proportionately. His story hits the headlines, and he becomes a national curiosity. He can no longer drive a car and has to give up his job working for his brother, Charlie (Paul Langton), who encourages him to make some money off his story by selling it to the national press. He begins keeping a journal, to be published as a record of his experiences. As things continue, Scott feels humiliated and expresses his shame by lashing out at Louise, who is reduced to tears of despair.
Then, it seems, an antidote is found for Scott's affliction: it arrests his shrinking when he is 36.5Â in (93Â cm) tall and weighs 52 pounds (24Â kg). However, he is told that he will never return to his former size unless a cure is found. He tries to accept the situation, but in a moment of extreme self-loathing, he runs out of the house, his first time being outside since he sold his story.
At a neighborhood coffee shop, he meets and becomes friends with a female midget named Clarice (April Kent), who is slightly shorter than him. She is appearing in a carnival sideshow in town and persuades him that life is not all bad being their size. Inspired, he begins to work on his book again. Two weeks later, during one of Scott's conversations with his new small friend, he suddenly notices he has become shorter than her, meaning the antidote has stopped working. Exasperated, he runs back home, ending his brief friendship with Clarice.
After becoming small enough to fit inside a dollhouse, Scott becomes more tyrannical with Louise, simultaneously wanting courage to end what he calls his "wretched existence" and hoping that his doctors can save him. He is attacked by his own cat one day while Louise is away on an errand, and winds up accidentally trapped in the basement of his home. Returning to find a bloody scrap of Scott's clothing, Louise tearfully assumes the cat ate him, and his undignified death is announced to the world. Assuming she is now a widow, Louise prepares to move.
Meanwhile, Scott goes through the odyssey of navigating his basement, which for him at his current size is a cavernous, inhospitable world. Most of his time is spent battling a voracious spider, his own hunger, and the fear that he may eventually shrink down to nothing. When the water heater bursts, Charlie and Louise come down to investigate; by now, however, Scott is so small that they cannot hear his screams for help. Louise moves out of the house. Scott ultimately kills the spider with a straight pin and collapses in exhaustion. Awakening, he finds he is now so small he can escape the basement by walking through the squares of a window screen. Scott accepts his fate and is resigned to the adventure of seeing what awaits him in even smaller realms. He knows he will eventually shrink to atomic size; but, no matter how small he becomes, he concludes he will still matter in the universe because, to God, "there is no zero." This thought gives him comfort, and he no longer fears the future.

Question: Who come down to investigate when the water heater bursts?
Answer: Charlie and Louise