Where Silence Has Lease

Nagilum was originally supposed to have been played by Richard Mulligan. That's how the character's name was developed.

SPOILER: Wesley Crusher disappears from the bridge with no explanation. He is at his station as the Captain sends Riker and Worf to the Yamato, but in the very next shot of the bridge, shortly after Riker and Worf, on the Yamato and try to contact the Enterprise again, Wesley is gone and in his place is Haskell. The reason becomes obvious a short time later when Nagilum kills Haskell, which is why he had to be there instead of Wesley.

Although it is peculiar that Wesley is no longer at the helm, it is not unheard of. Bridge crew are constantly leaving the bridge and having others replace them, so Wesley could have been called to another station or had another unknown reason for leaving (Troi, for example, also leaves the bridge between scenes--she is present when the Enterprise first encounters the "hole in space", but she is gone without explanation before Worf launches the first probe, and does not return again until after Riker and Worf return from the false Yamato). Wesley is also not an official member of Starfleet, so Capt. Picard may have replaced him because of the danger of the situation.

Alternatively, Wesley's replacement could have been effected by the being experimenting on the Enterprise.

Featured in Star Trek: First Contact Review (2009)