varchar to numeric error

Running the following query in SQL

select dbo.booking.PIN, dbo.arrest.ID, dbo.arrest.EXTDESC 

FROM dbo.arrest INNER JOIN dbo.BOOKING ON dbo.ARREST.ID = dbo.BOOKING.SYSID;

Gives me some results.

Msg 8114, Level 16, State 5, Line 1

Error converting data type varchar to numeric.

What am I doing wrong, and can someone help me debug the query? I can make basic queries but need some assistance with correcting this issue obviously.