The character of Seven of Nine has had a remarkable effect on the fortunes of Star Trek's fourth spin-off show, Voyager, since her introduction at the start of season four.

Jeri Ryan's portrayal of the Borg adopted by the lost Federation ship has also managed to polarise opinion in Trek fandom. Some view the introduction of a regular Borg crew member as a further unforgivable weakening of arguably Star Trek's most chilling creations. Others claim that Seven of Nine has revitalised the plots and character interaction in Voyager to an extent that makes the character unassailable.

There also appears to be widespread appreciation of Ryan for less considered reasons: something to do with the suit provided by the costume department and the priorities of the show's lighting director. Either way, there is enough enthusiasm for Seven of Nine to quash carping that her introduction may be no more than a cynical Paramount ploy to boost previously unspectacular ratings.

It is undeniable that there has been a pattern of quality episodes in the wake of Seven's debut: 'Scorpion - Part 2' (her first appearance), 'The Raven' and more recently 'Drone' and 'Dark Frontier' stand out particularly. Jeri Ryan's portrayal perfectly balances Seven's cold, meticulous and dispassionate Borg impulses with her slow recovery of human understanding and curiosity. It is credit to Ryan's skills that the exploration of the death of Seven's parents at the hands of the Borg and her absorption into the collective proved unexpectedly touching.

But she has also provided a new seam of humour, acting as deadpan foil to the enthusiasm of Harry Kim and Tom Paris, and facing the Doctor's more than professional interest in her with Borg aplomb.

Ultimately, Seven of Nine looks set to be one of Voyager's most popular and rewarding creations. It is intriguing to think how Star Fleet will react to Janeway's contentious new recruit when (or if?) the ship returns to Federation space.