Researchers developed a new method to track when and where a specific signaling protein called Alk is active in fruit fly hearts. They discovered that Alk is switched on in heart muscle cells of developing and adult flies, with a nearby protein called Jeb acting as the activating signal. When they increased Alk signaling artificially, flies developed irregular heartbeats and had shorter lifespans, especially under heat stress, revealing an important role for this protein in maintaining healthy heart function.