Matrix.

About Matrix

The Past Doctor Adventures were a series of spin-off novels based on the long running BBC science fiction television series Doctor Who and published under the BBC Books imprint. For most of their existence, they were published side-by-side with the Eighth Doctor Adventures. The novels regularly featured the First through Seventh Doctors. The Infinity Doctors had an ambiguous place in continuity and featured an unidentified incarnation of the Doctor. The Eighth Doctor co-starred with the Fourth Doctor in one novel (Wolfsbane) and, after the Eighth Doctor Adventures had ceased publication, a novel featuring the Eighth Doctor and set between two earlier Eighth Doctor Adventures was published within the Past Doctor series.