diff --git a/src/nancy/cli/__init__.py b/src/nancy/cli/__init__.py
index 6df259b..054bf3e 100644
--- a/src/nancy/cli/__init__.py
+++ b/src/nancy/cli/__init__.py
@@ -3,9 +3,7 @@ from loguru import logger
 
 from ..version import __version__
 
-from . import diff
-from . import record
-from . import show
+from . import check, diff, record, show
 
 from typing import Optional
 
@@ -50,6 +48,7 @@ def main(log_level: str) -> None:
     logger.add(sys.stderr, level=log_level)
 
 
+main.add_command(check.check_cli, name="check")
 main.add_command(diff.status, name="status")
 main.add_command(record.record_cli, name="record")
 main.add_command(show.show_cli, name="show")
diff --git a/src/nancy/cli/check.py b/src/nancy/cli/check.py
new file mode 100644
index 0000000..6bfc018
--- /dev/null
+++ b/src/nancy/cli/check.py
@@ -0,0 +1,143 @@
+import click
+from loguru import logger
+
+from .. import fs, store
+from .diff import print_diff
+
+from datetime import datetime
+import os
+import sys
+from typing import Any, List, Optional, Union
+import warnings
+
+
+@logger.catch
+def check(
+    store_path: Optional[Union[str, "os.PathLike[Any]"]] = None,
+    show_hashes: bool = False,
+    use_color: bool = True,
+) -> None:
+    """Unwrapped check command"""
+    start_time = datetime.now()
+
+    if store_path is None:
+        curdir = os.path.realpath(os.getcwd())
+        logger.info("Looking for store in {}", curdir)
+        store_path = store.find_store(curdir)
+        if store_path is None:  # If no store found, assume we're creating here
+            logger.error(
+                "Could not find nancy.db in any directory containing {}", curdir
+            )
+            sys.exit(1)
+        logger.info("Found store at {}", store_path)
+    s = store.Store(store_path)
+
+    cur = s.conn.cursor()
+
+    def columns(table: str, columns: List[str]):
+        cur.execute(f"SELECT {','.join(columns)} FROM {table}")
+        return cur.fetchall()
+
+    def oneresult(qry: str):
+        """Run a query that returns just one thing"""
+        cur.execute(qry)
+        (c,) = cur.fetchone()
+        return c
+
+    def count(table: str):
+        return oneresult(f"SELECT COUNT(*) FROM {table}")
+
+    local_uuid = oneresult('SELECT value FROM local_metadata WHERE key == "store_uuid"')
+    print(f'Local store has UUID "{local_uuid}"')
+
+    print(f"Stores ({count('store')}):")
+    for (storeid,) in columns("store", ["uuid"]):
+        print(f"  {storeid}")
+
+    print(f"Machines ({count('machine')}):")
+    for (sha256, name, machineid) in columns(
+        "machine", ["sha256", "hostname", "machine_id"]
+    ):
+        print(f"  {name:15} (sha256: {sha256}, machine-id: {machineid})")
+
+    print(f"Users ({count('user')}):")
+    cur.execute("SELECT user.sha256,fullname,username,hostname FROM user JOIN machine")
+    for sha256, full, uname, hostname in cur.fetchall():
+        print(f'  {uname + "@" + hostname:20} (fullname: {full}, sha256: {sha256}')
+
+    print(f"Programs ({count('program')}):")
+    cur.execute(
+        """
+        SELECT program.uuid,start_time,end_time,username,hostname,name,message
+        FROM program
+        JOIN environment JOIN user JOIN machine
+    """
+    )
+    for progid, starttime, endtime, uname, host, progname, message in cur.fetchall():
+        starttime = datetime.fromtimestamp(starttime)
+        endtime = datetime.fromtimestamp(endtime)
+        print(
+            f" {progname} "
+            f"(message:{message}, "
+            f"user:{uname}@{host}, "
+            f"start: {starttime} {starttime.tzinfo}, "
+            f"elapsed: {endtime - starttime})"
+        )
+
+    print(f"Environments: {count('environment')}")
+    print(f"Packages: {count('package')}")
+    print(f"Modules: {count('module')}")
+    print(f"Functions: {count('func')}")
+    print(f"Tasks: {count('task')}")
+    print(f"Files/Directories: {count('filedir')}")
+    print(f"File/Directory versions: {count('filedir_version')}")
+
+    # then find a listing covering all the expected paths
+    print("Checking for changes to filesystem. This may take a while...")
+    diff = s.diff()
+    if diff.A is None:
+        logger.warning(
+            f"No recorded entries in {store_path}. Have you run `nancy record` yet?"
+        )
+
+    if diff.is_modified():
+        logger.warning("Files have been modified:")
+        print_diff(diff)
+    else:
+        print("All files/directories are consistent with recorded versions.")
+
+
+@click.command()
+@click.option(
+    "-H",
+    "--show-hashes",
+    is_flag=True,
+    help="If given, prepend each line in the diff with the new file hash (SHA256).",
+)
+@click.option(
+    "--no-color",
+    is_flag=True,
+    help="If given, do not print any color output.",
+)
+@click.option(
+    "-s",
+    "--store",
+    type=str,
+    default=None,
+    help="Top-level of store. If omitted, use closest common parent directory "
+    "of given paths. If given the path to a non-store directory, a new "
+    "store is initialized there.",
+)
+def check_cli(
+    show_hashes: bool,
+    no_color: bool,
+    store: str,
+) -> None:
+    """
+    Check the store for altered files and other problems.
+    """
+    check(
+        show_hashes=show_hashes,
+        use_color=not no_color,
+        store_path=store,
+    )
diff --git a/src/nancy/fs.py b/src/nancy/fs.py
index ceb431c..c3f5c01 100644
--- a/src/nancy/fs.py
+++ b/src/nancy/fs.py
@@ -432,6 +432,15 @@ class FSDiff:
                 and Alatest.deleted == Blatest.deleted
             )
 
+    def is_modified(self):
+        """Return True only if there is a difference between A and B."""
+        if len(self.modified_children) > 0:
+            return True
+        if self.A is None or self.B is None:
+            return True
+        else:
+            return not self.__class__.compare(self.A, self.B)
+
     def filename(self) -> str:
         if self.A is not None:
             return self.A.filename