Brossmer was on duty in transporter room 3 when the Enterprise-D came to the aid of a damaged Romulan science vessel late in 2368. When Brossmer transported Lieutenant Commander Geordi La Forge and Ensign Ro Laren back to the ship with a graviton field generator, their patterns became unstable. Despite Brossmer's best efforts to abort the transport, the two officers were believed killed when their patterns disappeared.
In actuality, a chroniton field from an experimental interphase cloaking device caused Ro and La Forge to become phase cloaked. Brossmer later helped Lieutenant Commander Data pinpoint and eliminate the chroniton fields present aboard the Enterprise-D which were due to the presence of Ro and La Forge. She initiated an anyon sweep from a bridge science station, and in doing so unknowingly saved the ship - insisting that major systems should not be put to use until the sweep was finished, she convinced Captain Picard not to engage the warp drive, which had been sabotaged by the Romulans, buying enough time for Ro and La Forge to be phased back into normal space, at which point Geordi was able to reveal the sabotage (which, having gone back to the Romulan ship, he had overheard being discussed) and have the drive taken off-line until it was safe again. (TNG: "The Next Phase")