It
is using a note from the different key.
The music is introducing something new. For the first 40 seconds, it stays comfortably in Bb Major, touching occasionally its relative minor. From 0:35 on, it becomes more firmly attached to the minor key, and that chord -- the F# dim7, can also be thought D7b9 without the bass -- acts for the first time as the perfect fifth to the relative minor, giving us a first V-I progression in that key. Since the bass note, F#, is not part of the Bb major key, and as it comes as a progression from an F natural (= chromatic progression), I believe both elements contribute to the feeling that you are trying to describe.
Also 0:40 is the first time it introduce a new chord other than the straight major, the straight minor, and the minor seventh. Looking beyond that, at 0:50, it adds the suspension (Fsus2/A) -- this is actually a chord I use very often myself. Then, at 0:57, we hear for the first time the major seventh (EbMaj7). So all in all, I think the composer does a pretty good job to keep the music interesting over the first minute.