Kaplan took over Tuvok's tactical station while he was on an away mission to 1996 Earth. She reported to acting captain and fellow ensign, Harry Kim, an incoming EM signal from Earth that was directed at them. The message was a SETI greeting sent by Rain Robinson from the Griffith Observatory. When Kaplan inquired if she should respond, Kim told her that she should absolutely not. (VOY: "Future's End")
The same year, she and Commander Chakotay conducted a scouting mission of the Nekrit Expanse aboard a Class 2 shuttle looking for a faster way out of the nebula. On their return trip to Voyager, Kaplan admitted that they had become lost, noting that the Expanse had completely scrambling the shuttle's navigational readings.
Later, they received a Federation distress signal, which she has misidentified as having originated from Voyager. Landing on a nearby planet, they were attacked by one of the factions that later became part of the New Cooperative. Kaplan was killed during the attack. (VOY: "Unity")
Kaplan was later mentioned by Seven of Nine while reviewing Voyager's casualty list in 2377. According to Seven, although Kaplan died under Captain Janeway's command, Janeway had accepted her death. Contrarily, Seven felt that if she herself were to die, Janeway would not so easily accept the loss. (VOY: "Imperfection")
There were no particular script notes about Kaplan in any of the three episodes she appeared in, other than being referenced in the "Unity" script: "Ensign Kaplan (as seen in "Future's End")." Her first name was mentioned several years later by Seven in "Imperfection".